Peak In Magnetic Susceptibility Research Articles

The structure induced magnetic susceptibility peak to dip transition in the MoSe[formula omitted]Te[formula omitted]

The temperature independent magnetic susceptibility peak and dip were observed in the MoSe2−xTex. The magnetic susceptibility peak accompanies with ferromagnetism which originates from two electrons spin-parallelly stay at 4d orbit in the 1T@2H structure. It exhibits no relation between magnetic susceptibility dip and ferromagnetism. This originates from two electron spin-anti-parallelly stay at the 4d orbit in the 2H structure and forms a diamagnetism. The magnetic susceptibility peak to dip transition is understood as transition of ferromagnetism to diamagnetism that originates from the disappear of the 1T@2H phase.

Late Holocene high-resolution paleoenvironmental reconstruction from Beaver Lake in the northwest lowlands of the Olympic Peninsula, Washington (USA)

Fire is an essential component of the landscapes and forests of the Pacific Northwest, including the temperate rainforests of the Olympic Peninsula. Previous fire history reconstructions from the peninsula show that fire return intervals varied throughout the postglacial period, primarily in response to climatic changes and corresponding shifts in vegetation. However, much less is known about the fire history of the low-elevation forests of the Olympic Peninsula and the role of cultural fire regimes in these environments. The purpose of this study was to reconstruct the paleoenvironmental history of a low-elevation study site, Beaver Lake, located in the northwestern part of the peninsula. Using macroscopic charcoal, pollen, and sedimentological analyses of a ca. 3440-year-long record, we reconstructed a high-resolution record that shows fire activity was remarkably high during the late Holocene for an area considered part of a temperate rainforest. However, patterns of burning varied throughout the record, with the first third (ca. 3440 to 2350 cal yr BP) and last third (ca. 800 cal yr BP to the present day) recording much higher amounts of fire activity compared to the middle portion (ca. 2350 to 800 cal yr BP), which recorded very little fire activity. Larger and/or more severe fires that likely burned during multi-year droughts correlate with peaks in magnetic susceptibility and pollen trends that indicate substantial geomorphic responses and successional changes in forest structure following these events. Cooler temperatures and a wetter climate, indicated by nearby glacial advancements, may have staved off fire activity during the period of low fire activity. Cultural burning by the Indigenous tribes of the Olympic Peninsula likely contributed to the observed fire activity at Beaver Lake as nearby prairies were managed for resource procurement, indicated in particular by an increase in herbaceous morphotype charcoal during the past 800 years.

Comprehensive magnetic analysis of the tephras in Middle-Late Pleistocene loess records of Serbia, and implications for tephra identification, correlation and loess chronology

Tephras are highly valuable for achieving precise chronologies and secure correlations for sedimentary sequences. Rock magnetic investigations provide a simple, rapid tool for tephra identification especially for weathered tephra, cryptotephra (hidden tephra), thin and dispersed distal tephra. But so far, the most diagnostic magnetic properties for tephra identification and for differentiation of specific tephras are still uncertain. Three laterally continuous and representative tephras/cryptotephras embedded in Serbian loess deposits provide a rare opportunity to explore application of magnetic approaches in tephrostratigraphy. Systematic rock magnetic and petrographic comparison of tephra and its host loess reveal that the characteristic magnetic mineral of the studied tephras is moderate-Ti titanomagnetite of magmatic origin, with a dominant magnetic grain size of non-interacting single domain (SD) and pseudo-single domain (PSD) state. We identify the most diagnostic magnetic properties for tephra identification in loess and many other sediments. The Curie temperature of titanomagnetite is the most diagnostic property of tephras. A low-temperature alternating current (AC) magnetic susceptibility peak at ∼20–100 K is a sensitive indicator of coarse-grained titanomagnetite. SIRM-χfd and χARM-χfd plots can easily differentiate tephras from loess-paleosol sequences and possibly other pedogenesis-influenced sediments. Furthermore, our results suggest Curie temperatures can be a promising tool of regional tephra correlation. Our magnetic evidence and mineral composition analysis support the same origin of Tephra-L5 as Tephra-L4 from Alban Hills Volcanic District, possibly from the ∼457 ka eruption, which would promote a robust chronostratigraphic model of Danube loess.

Magnetic ordering in Co2+-containing layered double hydroxides via the low-temperature heat capacity and magnetisation study

The low-temperature heat capacity and the magnetisation of Co2+nAl3+ layered double hydroxides (LDH) with the cobalt-to-aluminium ratio n = 2 and 3 and intercalated with different anions have been studied in a wide range of magnetic fields up to 50 kOe. The heat capacity, C(T), was found to demonstrate a Schottky-like anomaly observed as a broad local maximum in the temperature dependence below 10 K. The effect is caused by a splitting of the ground-state Kramers doublet of Co2+ in the internal exchange field and correlates with magnetic ordering in these LDH. In low applied fields, the temperature-dependent dc magnetic susceptibility demonstrates a pronounced rise, which is associated with an onset of magnetic ordering. Both the heat capacity anomaly and the magnetic susceptibility peak are more pronounced for the LDH with n = 2 than for those with n = 3. This feature is associated with an excess of the honeycomb-like CoAl coordination (which corresponds to a 2:1 CoAl ordering) over the statistical cation distribution in Co2Al LDH, while a rather random cobalt-aluminium distribution is typical for Co3Al LDH. The temperature of the Schottky-like anomaly measured in a zero field is independent of the interlayer distance. Application of the magnetic field results in a widening of the anomaly range and a shift to higher temperatures. The observed experimental data are typical for a cluster spin glass ground state.

Santonian-Campanian Boundary Interval in the Kyunetsa Section, Western Srednogorie Zone, Bulgaria

The Kyunetsa section, 2.5 km west of Kosharevo, exposes mainly pelagic Upper Cretaceous marly limestones and marls of the Srednogorie Zone, part of the intermediate Balkanides in Bulgaria. The Melove Formation of Coniacian to early Campanian age involves a prominent Santonian-Campanian boundary interval of grey and reddish sediments, including CORBs (Cretaceous Oceanic Red Beds). The base of the Campanian can be discerned in bed 7c by the first rare (single) occurrence of the nannofossil Broinsonia (Aspidolithus) parca parca. A positive carbon isotope peak below, and a field magnetic susceptibility peak above may enhance correlation to other Tethyan sites such as the proposed GSSP at Bottaccione (Italy), the Postalm section (Austria) and the Mudurnu-Göynük Basin (Turkey).

Postglacial shelf erosion, riverine input and lake drainage in the eastern Kara Sea, Russia

Marine sediment core PS2719-1 represents a key sedimentary record for the reconstruction of the postglacial shelf evolution of the eastern Kara Sea west of the entrance to the Vilkitsky Strait. Sedimentological, chronological, geochemical, mineral magnetic and micropaleontological data were used to investigate the sedimentary evolution of the area in unprecedented detail. Four phases of sedimentation were identified, which are closely related to sea-level rise and input from the Yenisei and Taymyr Rivers. Sedimentation likely commenced directly after regional deglaciation prior to 13.6 cal ka BP. Basal sediments are coarse grained and rich in terrestrial organic matter, which points to shelf erosion as the dominating sedimentation process. Around 13.6 cal ka BP Yenisei River water masses reached the area, causing a shift in heavy mineral assemblages and a distinct peak in magnetic susceptibility. This phase was followed by increased sedimentation rates during the early Holocene, which were related to high sediment supply from Lake Taymyr, possibly due to the opening of an ice dam in the Lower Taymyra River area. These sediments are characterized by high terrestrial organic matter accumulation, a fine-grained composition, and a heavy mineral assemblage reflecting the sediment source on the Taymyr Peninsula. High burial rates are reflected by high Mn contents. The transition to modern conditions commenced already around 8.5 cal ka BP and were fully established at ca. 5 cal ka BP, being documented in mineral magnetic evidence and foraminiferal assemblages and are characterized by more marine conditions and a strong influence of the Yenisei River.

Holocene evolution and signature of environmental change of the Burullus lagoon (Nile Delta) deciphered from a long sediment record

This study presents high-resolution multi-proxy analyses of a well-dated sediment core (BR-1, 19.20 m long) retrieved from the Nile Delta, aiming to reconstruct the Holocene evolution of the Burullus lagoon. In particular, we focus on the morphodynamical processes, sediment provenances and related hydro-climatic changes. The Holocene strata of the lagoon coast comprise Early-Holocene marine transgressive facies and the Mid-Late Holocene retrogressive deltaic facies. Although BR-1 shows no river-channel facies, two peaks of magnetic susceptibility (MS) at ca. 8.0–7.0 ka (also associated with a high sedimentation rate of 50 mm/yr) and 3.5–2.0 ka evoke phases of greater morphodynamic influence of palaeo-Nile branches on the lagoon's development. Both dated peat layers (ca. 13 m and 8 m below MSL) and lagoon muds intercalated in BR-1, together with previously-dated peat strata were benchmarked relatively to MSL for the reconstruction of relative Holocene sea level in the study area. Our results show considerable land lowering on the Burullus coast indicated by a sea-level elevation, ca. 4–1 m lower than the one reconstructed along adjacent coastlines where less land subsidence occurred. The lagoon system began to form after ca. 6.0 ka in response to deceleration in sea-level rise and, being a shallower water body, both macrofauna (Cerastoderma glaucum etc.) and ostracods (Cyprideis torosa) of brackish-water nature emerged. In addition, geochemical data from BR-1 provide insights into environmental change in association with basin-wide hydro-climate fluctuations. Concomitant peaks in Fe/Al, Ti/Al and Cr/Al ratios (mafic origin), together with higher Zr/Al and Hf/Al ratios (felsic origin) before ca. 8.0 ka suggest sediment provenances derived from the White and the Blue Nile during the main African Humid Period (AHP). Since then, Ti/Al kept slightly ascending core-upwards with two pulses at 7.8–7.3 ka and 3.5–2.0 ka, which was asynchronous to Zr/Al and Hf/Al. This corroborates more sediments of basaltic origin transported to the delta coast after the main AHP due to southerly shift in the position of the ITCZ. The two periods of Ti/Al pulse are consistent with the MS peaks in BR-1, suggesting that palaeo-Nile branches remained active during 8.0–7.0 ka and 3.0–2.0 ka nearby.

Abrupt environmental changes during the last glacial cycle in Western Mediterranean (Formentera Island, Balearic archipelago, Spain)

A sedimentary sequence covering the entire last glacial cycle (period between Terminations I and II) outcrops along the south-eastern coast of Formentera Island. A detailed geomorphological, geological and sedimentological study, supported by geochemical, soil and soil-morphology analyses, magnetic susceptibility, phytolite content and luminescence dating (TL, OSL) allowed to reconstruct the environmental evolution of this coastal setting, and to frame it within the evolutionary pattern of the North Atlantic climate variability. Three highstands of sea level are identified in this island for MIS 5e, and a fourth one is attributed to MIS5a. MIS5 – MIS4 transition is characterized by soil development under a moist-warm climate and a descending sea level scenario. Aeolian units (72 ± 7 ka BP) developed during MIS4 under prevailing northerly winds that persisted until the beginning of MIS3, when new aeolian dunes (54 ± 5 ka BP) developed after a major sea-level lowstand. A sudden shift in prevailing winds occur within MIS3, when aeolian units (51 ± 4 ka BP) grew under the influence of S-SW winds and moister climate, evidenced by a dense root bioturbation. The greater influence of northerly winds is attributed to the weakening of Atlantic Meridional Overturning Current (AMOC) in North Atlantic, and enhancement of westerlies in NW Europe during colder periods. Periods of prevailing southerly winds and moister climate correlate well with warm Greenland Interstadials, and reinforcement of AMOC. Between 50 and 40ka, alluvial/colluvial sedimentary units punctuated by soil and calcrete development, witness the climatic variability recorded along this period in the North Atlantic. A sedimentary hiatus with erosion and calcrete development characterizes the transit between MIS3 and MIS2. Finally, a reddish alluvial sedimentary unit records a short span of humid and warm climate (soil development, peak in magnetic susceptibility, phytolite content) within MIS 2 (20 ± 2 ka BP – 17 + 2.4/-2.2) that contrast with the general climatic trend recorded in Western Mediterranean during the Last Glacial Maximum.

Rock magnetic properties of Grand Lake sediments as evidence of environmental changes during the last 60 000 years in North‐East Russia

Dansgaard–Oeschger events of the last glacial cycle are widely observed in the North Atlantic sector. In far northeast Asia, however, a lack of data means the presence or absence of these events is uncertain and, if present, the mechanisms that connect this region with the North Atlantic remain unresolved. A sediment record from Grand Lake, North‐East Russia (latitude 60°44′N, longitude 151°53′E), spans much of the last glacial cycle and shows strong variations in magnetic parameters. These variations are related to sedimentation changes that were likely influenced by the palaeoclimate. Rock magnetic properties of a 1020‐cm‐long sediment core were determined for four lithological units. Additionally, samples taken from across the modern catchment aided the interpretation of the magnetic properties of the down‐core sediments. Magnetic minerals in all sediment units consist of detrital, oxidized Ti‐poor titanomagnetites. Sediments of Holocene age (Unit 1) display the lowest values of magnetic susceptibility (MS), saturation magnetization (Js) and saturation remanence (Jrs), and reflect dilution by biogenic silica and organic matter. Variations of magnetic properties in Units 2, 3 and 4, which correspond to Marine Isotope Stages (MIS) 2, 3 and 4, respectively, parallel granulometric changes. Massive sediment structure, which characterizes Unit 3, has a coarser grain size and higher MS, Jrs and Js as compared with the laminated sediments of Unit 2 and Unit 4, suggesting higher‐energy catchment processes. Nine distinct peaks in MS, Js and Jrs within MIS 3 coincide with TiO2 minima and with high pollen percentages of trees and shrubs, supporting the conclusion that lake and catchment sediment processes are associated with fluctuating regional climate. While the dating is not resolved enough to be certain, the data are suggestive that these cycles correlate with Dansgaard–Oeschger events.

Fluvial magnetic susceptibility as a proxy for long‐term variations of mountain permafrost development in the Alp‐Carpathian region

Low field magnetic susceptibility (MS) records of 13 reference boreholes representing the whole Quaternary fluvial succession of the Great Hungarian Plain were correlated to develop regional stratigraphy. Data from 12 of the boreholes were published between 2016 and 2020, the Tiszainoka borehole is newly reported in this paper. Eleven magnetic susceptibility cycles, capped by the most emergent master MS peaks (MP) and bordered by susceptibility termination surfaces, have been correlated. Supported by the already evaluated palaeomagnetic reversals and instability events, MPs have been correlated to the cold stages of the Marine Isotope Stage (MIS) records. MPs represent MIS 104, 100, 98, 82, 60, 52, 34(−36) and 26 of increased heavy oxygen isotope value, constituting the significant Early Pleistocene glaciations, and MIS 18, 16, 12, 8, 6 and 2 mostly representing the substantial Middle and Upper Pleistocene European glaciation events. The interpretation of early postglacial fluvial MS maxima, which emphasizes the escape of weathering‐sensitive magnetic minerals from the catchment area triggered by the thawing of mountain permafrost, is confirmed by the correlation of MPs to the changes of the global ice volume. As a result, fluvial MS records can be considered as a proxy for mountain permafrost development in the catchment areas. Regional correlations confirmed that the Körös and Jászság Basins and the Makó Trough are sites of almost continuous fluvial records of the past 2600 ka. Thus, the Pannonian Quaternary fluvial succession is sufficiently complete to provide a satisfactory record of mountain permafrost development of the Alp‐Carpathian region, the latter being a globally relevant European representative of mid‐latitude mountain regions. The similarity of the Pannonian fluvial MS succession as a permafrost proxy to the marine ice‐rafted detritus (IRD) and Chinese loess/palaeosol MS records promises the possibility of comparative investigations of globally relevant proxy records and mid‐latitude mountain permafrost development.

Magnetic and Thermodynamic Properties of a Nanowire with Rashba Spin–Orbit Interaction

In this work, we have considered ballistic nanowires in the presence of gate-controlled Rashba spin–orbit interaction and an in-plane magnetic field. First, the energy expression of the nanowires was obtained. Then, the analytical relations for the mean energy, free energy, specific heat, entropy and magnetic susceptibility of the system were derived. It is found that the specific heat and magnetic susceptibility show peak structure in the presence of spin–orbit and magnetic field. The peak position of specific heat depends on the Rashba constant, Zeeman splitting parameter and the angle between magnetic field and the wire axis (θ). The peak of magnetic susceptibility disappears with increasing magnetic field and decreasing θ.

Identification of magnetic minerals in the peatlands cores from Lake Diatas West Sumatra, Indonesia

Peatlands in Lake Diatas can store various types of minerals. One of the mineral phases that can be found in peatlands are magnetic minerals derived from volcanic eruptions. This study was used to determine concentration of magnetic minerals found in peatlands. We applied the rock magnetism method, measuring the magnetic susceptibility of peat sediments to estimate the concentration of magnetic minerals within a peat core. Bartington Magnetic Susceptibility Meter type MS2C and dual frequency MS2B types, namely 470 Hz and 4.7 k Hz. In this study we analysed the magnetic susceptibility of core Diatas REP B at depths of 0-170 m and 240-720 m. From MS2B the values of low frequency magnetic susceptibility (χif )and high frequency magnetic susceptibility (χhf ) are obtained. The magnetic susceptibility values ranged from 365,2 × 10−8 m3/kg to 386,8 × 10−8 m3/kg and the value of magnetic susceptibility depends on frequency (%χfds ) range between 0,6 % - 1,3%. These low values indicate that almost no superparamagnetic grains are present. We identified a positive peak in magnetic susceptibility 386,8 × 10−8 m3/kg at 693 cm, whereas the lowest values were messured 365,2 × 10−8 m3/kg at 675 cm. Based on the value of magnetic susceptibility, the dominant magnetic mineral phases are Hematite (Fe2O3) and ilmenite (FeTiO3).

Multi-Proxy Approach for Identifying Heinrich Events in Sediment Cores from Hatton Bank (NE Atlantic Ocean)

A series of six gravity cores has been used to reconstruct the depositional history of Hatton Bank (Rockall Plateau, NE Atlantic Ocean). The cores have been studied for magnetic susceptibility (MS), geochemical composition, grain size distribution, and a semi-quantitative foraminiferal association. Two main interbedded facies have been described: (i) calcareous ooze; and (ii) lithogenous silt. The study reveals prominent peaks from the MS signal, silt, Mg/Ca, Fe/Ca, Al/Ca, and Rare Earth Elements normalised by Continental Crust (REE/CC), which are sensitive indicators for Heinrich events (H1, H2, H3, H4, and H5) and ash layers. These peaks may relate to alternations in dominance of the calcareous and lithogenic facies. The sediment displays a high percentage of carbonate in interglacial layers but is lithogenic-dominated in glacial stages. The layers with prominent lithic-rich and foraminifera-poor sediments (established as Heinrich layers) may be related to a possible palaeoclimatic effect, where freshwater discharged during iceberg melting may have reduced the formation of North Atlantic Deep Water (NADW). In the study area, the mean sedimentation rates for the last glacial as ~4.2 cm ka−1 and ~1.4 cm ka−1 for the last ~18 ka (interglacial period) have been estimated. Besides this evidence, Fe/Ca and MS peaks may reflect the presence of basalt, either introduced through ice-rafting or transported and redistributed by bottom currents in the study area. Certain indices, including MS and Fe/Ca, are proposed as good proxies for detecting Heinrich events and ash layers in the Hatton Bank sediments and, in consequence, are parameters that can be used to infer strengthened/weakened NADW formation, according to stadials/interstadials. Moreover, we suggest that the northernmost boundary of the area with evidence of Heinrich events may be situated around 57°38′ N in the Hatton–Rockall area, at least for H4, based on the variation of the Mg/Ca and Fe/Ca curves.

Influence of Crystallite Size on the Magnetic Order in Semiconducting ZnCr2Se4 Nanoparticles.

Structural, electrical, magnetic, and specific heat measurements were carried out on ZnCr2Se4 single crystal and on nanocrystals obtained from the milling of this single crystal after 1, 3, and 5 h, whose crystallite sizes were 25.2, 2.5, and 2 nm, respectively. For this purpose, the high-energy ball-milling method was used. The above studies showed that all samples have a spinel structure, and are p-type semiconductors with less milling time and n-type with a higher one. In turn, the decrease in crystallite size caused a change in the magnetic order, from antiferromagnetic for bulk material and nanocrystals after 1 and 3 h of milling to spin-glass with the freezing temperature Tf = 20 K for the sample after 5 h of milling. The spin-glass behavior for this sample was derived from a broad peak of dc magnetic susceptibility, a splitting of the zero-field-cooling and field-cooling susceptibilities, and from the shift of Tf towards the higher frequency of the ac susceptibility curves. A spectacular result for this sample is also the lack of a peak on the specific heat curve, suggesting a disappearance of the structural transition that is observed for the bulk single crystal.

Coexistence of localized and heavy itinerant states in antiferromagnetic CePtGe2

Two conflicting ground states, i.e., an antiferromagnetic ground state at 3.8 K and a ferromagnetic ground state at 5.1 K, have been reported for $\mathrm{CePtG}{\mathrm{e}}_{2}$, which has two nonequivalent crystallographic Ce sites. In this study, we have prepared polycrystalline and single-crystalline $\mathrm{CePtG}{\mathrm{e}}_{2}$ samples and measured their magnetization, specific heat, resistivity, and Seebeck coefficient. The observed bend in resistivity, peak in magnetic susceptibility, and \ensuremath{\lambda}-type anomaly in specific heat at ${T}_{N}=3.8\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ and the metamagnetic transition in this $\mathrm{CePtG}{\mathrm{e}}_{2}$ suggest antiferromagnetism at low temperatures. No evidence of ferromagnetic order was found in the studied temperature range, indicating possible crystal polymorphism with ferromagnetic character. The large susceptibility around ${T}_{N}$ and the Schottky-type specific heat indicate a well-localized $f$-electron state. However, the large residual \ensuremath{\gamma} and \ensuremath{\chi}(0) indicate an itinerant heavy $f$-electron state. These findings suggest the coexistence of localized and heavy itinerant states corresponding to $f$ electrons at the two Ce sites in this antiferromagnetic $\mathrm{CePtG}{\mathrm{e}}_{2}$. The field dependence of magnetization indicates a sudden increase in magnetization at weak magnetic fields $(\ensuremath{\sim}0.2\phantom{\rule{0.16em}{0ex}}\mathrm{T})$, followed by a plateau at fields above 0.2 T, resulting in a possible different polarized metamagnetic state via interaction between localized and itinerant $f$ electrons.

Late Pleistocene site formation and paleoclimate at Lapa do Picareiro, Portugal

AbstractThe cave site of Lapa do Picareiro, Portugal contains a deep (~10 m) sedimentary sequence representing much of the Middle and Upper Paleolithic, with abundant animal bones, lithic/bone/shell artifacts, and charcoal/ash in hearths. A deposition model based on 49 radiocarbon ages demonstrates average sedimentation rates of 0.1–0.3 mm a −1 between 9 and 45 ka. Extrapolation suggests an age at the base of the excavation of 65–78 ka. The cave sediments are primarily limestone éboulis derived from roof spalling, and muddy fine sediment derived from weathered soil infiltrating through bedrock joints and crevices. Bone preservation in the cave is good and disturbance by bioturbation, dissolution, or erosional processes appears to be limited. Most sedimentological parameters vary conservatively with depth, indicating stable sediment sources over time. Several parameters show good agreement with paleoclimate records over the radiocarbon‐dated section. The cold‐arid Heinrich stadials are represented by coarse‐clast beds with little fine sediment and magnetic susceptibility minima, and mild Greenland interstadials correspond with muddy beds and sharp peaks in magnetic susceptibility. This study complements ongoing archaeological excavation at the site and confirms that the sequence has the proper age, resolution, and preservation to inform on Late Pleistocene cultural and climatic transitions.

Magnetic properties of ZnxFe3−xO4 nanoparticles: A competition between the effects of size and Zn doping level

Abstract The nanoparticles of the ZnxFe3−xO4 (0 ≤ x ≤ 0.5) ferrites have been synthesized using a simple co-precipitation method under air atmosphere at room temperature. The Fourier transform infrared spectroscopy and X-ray diffraction patterns confirm the formation of spinel mono-phase structure in all the samples. The results show that the crystallite size relates to the cationic distribution. The cation distribution is derived from the X-ray diffraction patterns enabling determination of ion coordination, ion occupancy and unit cell parameter. The magnetic hysteresis loops reveal that the magnetization increases with Zn content up to x = 0.3 and then decreases with further Zn doping, which is explained in terms of the competition between the influence of crystallite size and cations distribution (site occupancies). The thermal behavior of magnetization for the selected x = 0.3 sample is described by a modified Bloch law, based on the spin wave excitations in the particle core. Furthermore, the temperature of the AC magnetic susceptibility peak increases up to 0.3 Zn, then decreases by further Zn doping. The frequency dependence of AC magnetic susceptibility indicates the presence of strong interparticle interactions resulting in a superspin glassy state. The experimental evidence of memory effect in x = 0.3 sample further confirms the frustrated magnetic state in the compounds. The potential application of these materials for hyperthermia based therapy has been estimated. The results show that in the studied series, Zn0.3Fe2.7O4 with highest loss power is the best candidate for this therapy.

Возможности магнитного псевдорезонанса в изучении тонких ферромагнитных пленок с одноосной магнитной анизотропией

AbstractPossibilities of magnetic pseudoresonance (a non-resonance peak of magnetic susceptibility) were studied and compared with the ferromagnetic resonance (FMR) in measuring the parameters of thin ferromagnetic films with in-plane uniaxial magnetic anisotropy. The measurements were conducted with two characteristic samples of ferromagnetic films showing this effect. A Q -meter operating at a frequency near 300 MHz (for pseudoresonance) and a standard X -band magnetic resonance spectrometer (for FMR) were used. The Q -meter working at 300 MHz was shown to detect reliably the magnetic pseudoresonance in both epitaxial and polycrystalline films. It was found that the accuracy of determination of the magnetic anisotropy field and orientation of the easy magnetization axis provided by the pseudoresonance method is as good as with FMR, and in some cases the pseudoresonance method gives additional information.

Capabilities of Magnetic Pseudoresonance in Studies of Thin Ferromagnetic Films with Uniaxial Magnetic Anisotropy

Possibilities of magnetic pseudoresonance (a non-resonance peak of magnetic susceptibility) were studied and compared with the ferromagnetic resonance (FMR) in measuring the parameters of thin ferromagnetic films with in-plane uniaxial magnetic anisotropy. The measurements were conducted with two characteristic samples of ferromagnetic films showing this effect. A Q-meter operating at a frequency near 300 MHz (for pseudoresonance) and a standard X-band magnetic resonance spectrometer (for FMR) were used. The Q-meter working at 300 MHz was shown to detect reliably the magnetic pseudoresonance in both epitaxial and polycrystalline films. It was found that the accuracy of determination of the magnetic anisotropy field and orientation of the easy magnetization axis provided by the pseudoresonance method is as good as with FMR, and in some cases the pseudoresonance method gives additional information.

Magnetostratigraphy and paleoenvironmental events recorded in a late Cenozoic sedimentary succession in Huaibei Plain, East China

The thick late Cenozoic deposits of Huaibei Plain provide a record of paleoenvironmental changes in the northern and southern transitional zone of eastern China, and of the evolution of the Asian monsoon system. A detailed magnetostratigraphic study of the Huainan (HN, 481.45-m deep) drill core from the center of Huaibei Plain reveals a magnetic polarity sequence from chron C4n.2n to chron C1n, spanning the interval from ∼8 Ma to the present; it is the first reliable magnetostratigraphic chronology for the late Miocene to present for Huaibei Plain. The stratigraphic sequence contains three intervals characterized by major peaks in magnetic susceptibility (at depths of 58.8 m, 108.0 m and 312.4 m), which can be used as isochronous marker beds for regional stratigraphic correlations in Huaibei Plain. Major changes in sediment grain-size occur at 7.0 and 1.7 Ma, corresponding to pronounced environmental shifts, which we consider reflect the respective strengthening of the South Asian summer monsoon and East Asian winter monsoon at these times.