Specific Magnetic Susceptibility Research Articles

Crystal structure and magnetic susceptibility of (CuInSe2)1 − x (2MnSe) x

The crystal structure of samples in the (CuInSe2)1 − x (2MnSe) x system at room temperature and their magnetic susceptibility in the temperature range 77–1000 K are investigated. It is established that compositions with concentrations 0≤ x ≤ 0.2 form solid solutions with a tetragonal structure, space group I $$ \bar 4 $$ 2d (122). The specific magnetic susceptibility χ of samples with 0.1 ≤ x ≤ 0.4 at 77 K lies in the range 9 × 10−4−1.6 × 10t-3cm3/g. The temperature dependence of the inverse magnetic susceptibility of the sample with x = 0.4 suggests the presence of a component with antiferromagnetic ordering and a reliably measured Neel temperature that is characteristic of MnSe. The dependences χ = f(T) of the compositions with x = 0.1, 0.2, 0.3, and 0.4 indicate the occurrence of magnetic phase transitions with a change in the spin state.

Specific heat and magnetic susceptibility of the spinelsGeNi2O4andGeCo2O4

J. C. Lashley,1 R. Stevens,2 M. K. Crawford,3 J. Boerio-Goates,2 B. F. Woodfield,2 Y. Qiu,4,5 J. W. Lynn,4 P. A. Goddard,1,6 and R. A. Fisher1 1Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA 2Department of Chemistry and Biochemistry, Brigham Young University, Provo, Utah 84602, USA 3Central Research and Development Department, DuPont, E400/5424, Wilmington, Delaware 19880, USA 4NIST Center for Neutron Research, Gaithersburg, Maryland 20899, USA 5Department of Materials Science and Engineering, University of Maryland, College Park, Maryland 20742, USA 6Clarendon Laboratory, University of Oxford, Parks Road, Oxford OX1 3PU, United Kingdom Received 29 January 2008; revised manuscript received 29 April 2008; published 11 September 2008

Concentration phase transition near the stoichiometric composition of vanadium monoxide VO1.00

The concentration dependences of the magnetic susceptibility and lattice parameter of cubic vanadium monoxide have been measured in the composition range from VO0.81 to VO1.07. Near the stoichiometric composition VO1.00, the concentration dependences exhibit a stepwise increase in the specific magnetic susceptibility (by approximately 0.7 × 10−6 cm3/g) and lattice constant (by about 0.002 nm). These effects can be related to the concentration phase transition, which occurs in vanadium monoxide with a change from a substoichiometric composition to superstoichiometric. At such a transition, along with a decrease in the concentration of oxygen vacancies, tetrahedrally coordinated vanadium interstitials are formed, as a result of which the B1 structure changes to a more complex cubic phase structure with the same space group Fm-3m.

Spin-density-wave anomaly at 140 K in the ternary iron arsenideBaFe2As2

The ternary iron arsenide ${\text{BaFe}}_{2}{\text{As}}_{2}$, with the tetragonal ${\text{ThCr}}_{2}{\text{Si}}_{2}$-type structure, exhibits a spin-density-wave (SDW) anomaly at 140 K, very similar to LaFeAsO, which is the parent compound of the iron arsenide superconductors. ${\text{BaFe}}_{2}{\text{As}}_{2}$ is a poor Pauli-paramagnetic metal and undergoes a structural and magnetic phase transition at 140 K, accompanied by strong anomalies in the specific heat, electrical resistance, and magnetic susceptibility. In the course of this transition, the space-group symmetry changes from tetragonal $(I4/mmm)$ to orthorhombic $(Fmmm)$. $^{57}\text{F}\text{e}$ M\"ossbauer spectroscopy experiments show a single signal at room temperature and full hyperfine field splitting below the phase-transition temperature (5.2 T at 77 K). Our results suggest that ${\text{BaFe}}_{2}{\text{As}}_{2}$ can serve as a parent compound for oxygen-free iron arsenide superconductors.

Valence states and metamagnetic phase transition in partiallyB-site-disordered perovskiteEuMn0.5Co0.5O3

The valence states of transition metals were studied by measuring the x-ray absorption spectra at both $\mathrm{Mn}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ and $\mathrm{Co}\phantom{\rule{0.2em}{0ex}}{L}_{2,3}$ edges of partially $B$-site-disordered perovskite $\mathrm{Eu}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$. By comparison with analogous spectra in various Co- and Mn-based compounds, the divalent state of the Co ions and the tetravalent state of the Mn ions were established analogous to ${\mathrm{Mn}}^{4+}∕{\mathrm{Co}}^{2+}$ charge ordering found by Dass and Goodenough [Phys. Rev. B 67, 014401 (2003)] in $\mathrm{La}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$. The specific heat and magnetic susceptibility data indicate the formation of the magnetically ordered state at ${T}_{C}\ensuremath{\sim}120\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. The first-order metamagnetic transitions seen in $\mathrm{Eu}{\mathrm{Mn}}_{0.5}{\mathrm{Co}}_{0.5}{\mathrm{O}}_{3}$ at $T<{T}_{C}$ suggest the existence of antiferromagnetic and/or paramagnetic clusters embedded into the ferromagnetic matrix.

Spin structure and first-order transition ofGdIn3: Near-surface magnetism, buried amplitude-modulated phase, and interface delocalization

A resonant x-ray magnetic diffraction study was performed for pure and (Cd,Ga)-doped $\mathrm{Gd}{\mathrm{In}}_{3}$ single crystals with cubic structure. All studied samples show an equal-magnitude antiferromagnetic spin structure with propagation vector $\stackrel{P\vec}{\ensuremath{\tau}}=[\frac{1}{2},\frac{1}{2},0]$ at low temperatures, corresponding to a parallel spin propagation along the $\stackrel{P\vec}{c}$ direction (normal to the studied surfaces) and antiparallel propagation along $\stackrel{P\vec}{a}$ and $\stackrel{P\vec}{b}$. A complex magnetic behavior in the submicrometric near-surface region (NSR) was found close to ${T}_{N}^{\mathit{\text{bulk}}}\ensuremath{\sim}44\phantom{\rule{0.3em}{0ex}}\mathrm{K}$. For both pure and substituted samples, a fairly strong signal from the equal-magnitude magnetic phase was found to survive above ${T}_{N}^{\mathit{\text{bulk}}}$ and abruptly disappears at ${T}_{N}^{\mathit{NSR}}\ensuremath{\sim}{T}_{N}^{\mathit{\text{bulk}}}+0.7\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, indicating that the NSR may show a larger ${T}_{N}$ than the bulk for all studied samples. For the pure compound only, satellite peaks consistent with an amplitude-modulated magnetic phase with a wavelength of $380\phantom{\rule{0.3em}{0ex}}\mathrm{\AA{}}$ were found between ${T}_{N}^{\mathit{\text{bulk}}}$ and ${T}_{N}^{\mathit{NSR}}$. A successful fit of the scattering profile around several magnetic Bragg positions and photon energies, using a simple phase coexistence model, confirmed that the amplitude-modulated phase develops underneath the most superficial region showing the equal magnitude structure. The evolution of the magnetic scattering profile on cooling indicates that the interface between equal-magnitude and amplitude-modulated phases diverges towards the bulk as $T\ensuremath{\rightarrow}{T}_{N}^{\mathit{\text{bulk}}}$ from above. A detailed analysis of the magnetic scattering, as well as the existence of a single bulk transition within the experimental sensitivity of our specific heat and magnetic susceptibility measurements, in contrast to the rich behavior shown by the near-surface region, indicates that the amplitude-modulated phase is not bulk representative, being actually sandwiched between the bulk paramagnetic and the equal-magnitude phases. Depth-temperature phase diagrams for pure and (Ga,Cd)-doped $\mathrm{Gd}{\mathrm{In}}_{3}$ are drawn on the basis of our results, which are discussed in terms of a three-phase coexistence scenario theoretically proposed for first-order transitions in the NSR.

Ambient-pressure bulk superconductivity deep in the magnetic state ofCeRhIn5

Specific heat, magnetic susceptibility, and electrical transport measurements were performed at ambient pressure on high quality single-crystal specimens of $\mathrm{Ce}\mathrm{Rh}{\mathrm{In}}_{5}$ down to ultralow temperatures. We report signatures of an anomaly observed in all measured quantities consistent with a bulk thermodynamic phase transition to a superconducting state at ${T}_{c}=110\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$. Occurring far below the onset of antiferromagnetism at ${T}_{N}=3.8\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, this transition appears to involve a significant portion of the available low-temperature density of electronic states, exhibiting an entropy change in line with that found in other members of the 115 family of superconductors tuned away from quantum criticality.

A refined biomonitoring study of airborne particulate matter pollution in Rome, with magnetic measurements onQuercus Ilextree leaves

SUMMARY Elevated levels of airborne particulate matter (PM) are a current problem for air quality in many major metropolitan areas. Many European cities have tightened the PM limits in the air, due to advances in monitoring PM levels. In order to establish guidelines for monitoring and curbing anthropogenic PM output, a better understanding of its origin, composition and diffusion is required. Biomonitoring of magnetic properties of tree leaves has been suggested previously to be a good approach to measure pollution levels in cities both in space and time. We report on a magnetic biomonitoring study of PM in the city of Rome, conducted from 2005 October to December. We collected approximately 180 different sample sets of tree leaves of Quercus ilex, an evergreen oak widely distributed in Rome, at 112 different locations. Specific magnetic susceptibility χ of the leaf is used as a fast, easy and cost-effective proxy to assess levels of primary anthropogenic airborne PM pollution. Highly polluted areas correlate with high traffic areas, with an average susceptibility value of χ = 3.2 × 10 −7 m 3 kg −1 .L ow traffic zones are characterized by values more than an order of magnitude lower at χ = 1.4 × 10 −8 m 3 kg −1 , and the background magnetic susceptibility is around χ = 2.6 × 10 −9 m 3 kg −1 . The data show that distance dependence from the source is the most significant factor for the concentration of magnetic PM, and that pollution levels and sources can be reliably delineated by measuring magnetic susceptibility values on tree leaf samples of Q. ilex. A new protocol for magnetic susceptibility measurements is proposed, in order to account for changes due to water evaporation in the leaves as a function of time after collection of the samples. Additional magnetic analyses, such as acquisition of artificial remanences and hysteresis properties, were used to characterize the mineralogy and grain size of the magnetic PM. The results indicate that the population of ferrimagnetic phases have a homogenous composition and grain size throughout the investigated area.

Two-Step Magnetic Ordering in Quasi-One-Dimensional Helimagnets: Possible Experimental Validation of Villain’s Conjecture about a Chiral Spin Liquid Phase

Low-temperature specific heat, magnetic susceptibility, and zero-field muon spin resonance (microSR) measurements have been performed in the quasi-one-dimensional molecular helimagnetic compound Gd(hfac)3NITEt. The specific heat presents two anomalies at T(0)=2.19+/-0.02 K and T(N)=1.88+/-0.02 K, which both disappear upon the application of a weak magnetic field. Conversely, magnetic susceptibility and muSR data show the divergence of two-spin correlation functions only at T(N)=1.88+/-0.02 K. These results suggest an experimental validation of Villain's conjecture of a two-step magnetic ordering in quasi-one-dimensional XY helimagnets; i.e., the paramagnetic phase and the helical spin solid phase are separated by a chiral spin liquid phase, where translational invariance is broken without violation of rotational invariance.

Magnetization plateau in diamond chains with delocalized interstitial spins

Several low-dimensional magnetic compounds exhibit magnetization plateaus as a result of the interplay between frustration and quantum fluctuations. Here, we investigate the thermodynamic properties of diamond chains on which competing interactions emerge from the local quantum hopping of interstitial $S=1∕2$ spins which are intercalated between nodal Ising spins. Using an exact diagonalization and the decoration-iteration transformation, we compute the temperature and external field dependences of the magnetization, specific heat, susceptibility, and the full ground state phase diagram. Magnetization plateaus of $1∕3$ are observed and related to field-driven transitions among four possible ground states: saturated paramagnetic, unsaturated paramagnetic, ferrimagnetic, and nodal antiferromagnetic. There is a range of hopping amplitudes and exchange mismatches for which the $1∕3$ magnetization plateau occurs between finite values of the external field. The specific heat and magnetic susceptibility also show signatures of the competition between the possible ground states.

Low Temperature Anomalies in the Specific Heat and Magnetic Susceptibility of Na0.7CoO2Samples

Low Temperature Anomalies in the Specific Heat and Magnetic Susceptibility of Na_0.7CoO₂Samples

Physical Properties of the Noncentrosymmetric SuperconductorMg10Ir19B16

Specific heat, electrical resistivity, and magnetic susceptibility measurements on a high quality sample of Mg10Ir19B16 provide a self-consistent determination of its superconducting properties. They indicate that Mg10Ir19B16 is a type-II superconductor [T{C}=4.45 K, kappa(0) approximately 20], with an electron-phonon coupling constant lambda{ep}=0.66. An analysis of the T-dependent specific heat shows that superconducting properties are dominated by an s-wave gap (Delta=0.7 meV). Point contact tunneling data provide evidence for multiple superconducting gaps, as expected from strong asymmetric spin-orbit coupling.

Spin Gap State ofS= 1/2 Heisenberg Antiferromagnet YbAl3C3

YbAl 3 C 3 has been investigated in detail, which was previously reported to show an antiferroquadrupolar (AFQ) ordering at an extremely high ordering temperature of 80 K. The present study has revealed that the specific heat, magnetic susceptibility, and electrical resistivity of the single crystalline YbAl 3 C 3 clearly exhibit the characteristic features of the first order transition around 77 K. In addition, we have discovered that LuAl 3 C 3 also exhibits a sharp peak in the specific heat around 110 K, which most likely corresponds to the 77 K transition of YbAl 3 C 3 . Therefore, the 77 K transition of YbAl 3 C 3 is considered to be irrelevant to the nature of the 4 f -electrons such as the AFQ ordering but is ascribed to a structural one. Low temperature physical properties of YbAl 3 C 3 below 77 K is indicative of a spin gap and a nonmagnetic ground state. A new model is proposed, in which the adjacent spins on the triangular lattice of Yb 3+ ions are antiferromagnetically coupled to form a dimer by the structural transition at 77 K. The spin gap behavior at low temperatures can be well explained by an isolated dimer model with a singlet–triplet energy gap of about 15 K.

Monte Carlo analysis of critical properties of the two-dimensional randomly site-diluted Ising model via Wang–Landau algorithm

The influence of random site dilution on the critical properties of the two-dimensional Ising model on a square lattice was explored by Monte Carlo simulations with the Wang–Landau sampling. The lattice linear size was L = 20 – 120 and the concentration of diluted sites q = 0.1 , 0.2 , 0.3 . Its pure version displays a second-order phase transition with a vanishing specific heat critical exponent α , thus, the Harris criterion is inconclusive, in that disorder is a relevant or irrelevant perturbation for the critical behaviour of the pure system. The main effort was focused on the specific heat and magnetic susceptibility. We have also looked at the probability distribution of susceptibility, pseudocritical temperatures and specific heat for assessing self-averaging. The study was carried out in appropriate restricted but dominant energy subspaces. By applying the finite-size scaling analysis, the correlation length exponent ν was found to be greater than one, whereas the ratio of the critical exponents ( α / ν ) is negative and ( γ / ν ) retains its pure Ising model value supporting weak universality.

Coexistence of localized and delocalized f-electrons inα−YbPdSnfrom thermodynamic and transport measurements

We report the specific heat, magnetic susceptibility, and magnetization as well as resistivity of hexagonal $\ensuremath{\alpha}\text{\ensuremath{-}}\mathrm{Yb}\mathrm{Pd}\mathrm{Sn}$ polycrystals down to temperatures $T$ of $50\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$ and fields up to $12\phantom{\rule{0.3em}{0ex}}\mathrm{T}$. In the susceptibility $\ensuremath{\chi}(T)$, several different temperature regimes can be distinguished. For $300\phantom{\rule{0.3em}{0ex}}\mathrm{K}>T>170\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, a Curie-Weiss-like behavior is obtained with the effective moments close to that of ${\mathrm{Yb}}^{3+}$. The large Weiss temperature ${\ensuremath{\Theta}}_{H}\ensuremath{\approx}150\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ and the leveling off of $\ensuremath{\chi}$ toward low $T$ are indicative of valence fluctuations. Around $30\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, crystal-field excitations manifest themselves in features of $\ensuremath{\chi}(T)$ and the resistivity $\ensuremath{\rho}(T)$. For $5\phantom{\rule{0.3em}{0ex}}\mathrm{K}>T>0.2\phantom{\rule{0.3em}{0ex}}\mathrm{K}$, a Curie-Weiss behavior with ${\ensuremath{\mu}}_{\mathit{eff}}=1.27{\ensuremath{\mu}}_{B}∕\mathrm{Yb}$ atom and ${\ensuremath{\Theta}}_{L}=0.41\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ is found, signaling the occupation of the lowest crystal-field doublet. A sharp maximum in $\ensuremath{\chi}(T)$ and in the specific heat $C(T)$ indicates antiferromagnetic ordering at $250\phantom{\rule{0.3em}{0ex}}\mathrm{mK}$. The specific-heat peak develops into a broadened Schottky anomaly in moderate magnetic fields. The sizable linear specific-heat coefficient $\ensuremath{\gamma}=68\phantom{\rule{0.3em}{0ex}}\mathrm{mJ}∕\text{mole}\phantom{\rule{0.2em}{0ex}}{\mathrm{K}}^{2}$ is attributed to valence fluctuations. Likewise, the magnetization at 10 and $2.3\phantom{\rule{0.3em}{0ex}}\mathrm{K}$ measured up to $12\phantom{\rule{0.3em}{0ex}}\mathrm{T}$ can be decomposed into a contribution of delocalized electrons and localized magnetic moments. The data can be consistently interpreted in terms of a two-fluid model with $\ensuremath{\sim}6%$ localized and $\ensuremath{\sim}94%$ delocalized moments derived from (nearly) trivalent Yb.

Liver Iron Measurement by SQUID Biosusceptometry Compared to Liver Biopsy: A More Accurate Definition of Optimal Iron Range.

The “Optimal Liver Iron” range in iron overloaded patients with thalassemia has been established by Olivieri and Brittenham (Blood, 1997) as 1–2.2 mg/g wet weight liver using direct measurement or calculated as 3.2 to 7 mg/g dry liver weight based on a 3.33 correction factor for body water. This report describes the relationship between liver iron concentration (LIC) measured by SQUID biosusceptometry (BLS, wet weight) compared to liver biopsy (dry weight), in patients with thalassemia (THAL) or sickle cell disease (SCD). A total of 38 chronically transfused patients (THAL n=19, SCD n=19) were prospectively assessed for LIC measured by BLS and liver biopsy within 2 month of each other. Most BLS results were submitted to data repository before receiving iron concentration from liver biopsy. LIC was measured by a low temperature SQUID biosusceptometer system (Ferritometer®) under the standardized Hamburg-Torino-Oakland protocol. Iron in fresh tissue and paraffin embedded liver biopsy samples was measured at Mayo clinics by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Subjects ranged in age from 5 to 40 years (median: 18 y). Median LIC (n=38) measured by SQUID was 1777 (365–4883) [mg/g wet weight], median LIC by biopsy (fresh tissue) was 10861(1854–32864) [mg/g dry weight]. After excluding the subjects with BMI>30 kg/m2 (n=5), the Spearman rank correlation between wet weight LIC assessed by BLS and dry weight LIC from fresh tissue sample measured by ICP-MS was highly significant (RS=0.90, p<0.0001). No significant difference between fresh tissue and paraffin embedded LIC values was observed. The agreement between BLS and fresh tissue biopsy was tested by Bland-Altman plots. After normalization, no significant proportional or zero bias was visible. The 95% limits of agreement between SQUID-BLS and biopsy LIC values were found between −56% (or –6733 μg/g) and 48% (or 7027 μg/g). This kind of agreement is similar to the results achieved with MRI-R2 by St. Pierre et al (Blood, 2005)(–56% and 50%), however, BLS is a totally independent method relying only on the specific magnetic susceptibility of the hemosiderin-ferritin iron complex. The conversion factor between the two methods (LIC by fresh tissue biopsy vs. LIC by BLS) obtained from a weighted linear regression with zero intercept (Marquardt algorithm) was 6.1 ± 0.3 (R2 = 0.86–0.88, cn2 = 2.3–2.6). Using this conversion factor, the recommended “optimal range” for liver iron in patients with thalassemia major should be considered as 6–13.2 mg/g dry weight liver rather than the generally accepted 3.2–7 mg/g dry weight liver.

Kagome antiferromagnet: A Schwinger-boson mean-field theory study

liquid state for spin S = 1/2 and a mixed state with both q = 0 and p 3 × p 3 orders for spin S > 1/2. We emphasize that the mixed state exhibits two sets of peaks in the static spin structure factor. And for the case of spin S = 1/2, the gap value we obtained is consistent with the previous numerical calculations by other means. We also discuss the thermodynamic quantities such as the specific heat and magnetic susceptibility at low temperatures and show that our result is in a good agreement with the Mermin-Wagner theorem.

Occurrence of magnetism in [formula omitted] ( [formula omitted], Ir)

The physical properties of CeM ( In 1 - x Hg x ) 5 ( M = Rh , Ir) including specific heat and magnetic susceptibility are reported. Two magnetic phases exist in CeRhIn ( In 1 - x Hg x ) 5 with some evidence of a change from incommensurate magnetic order to a commensurate structure near 10% nominal Hg substitution. In CeIr ( In 1 - x Hg x ) 5 , an antiferromagnetic quantum critical point near x = 3 % (followed by robust long-range antiferromagnetism for x > 5 % ) appears to be separated from superconductivity in CeIrIn 5. The multitude of magnetic ground states observed in the CeM ( In 1 - x Hg x ) 5 materials is quite sensitive to doping and magnetic fields.

Bose–Einstein Condensation of Quasi-Two-Dimensional Frustrated Quantum Magnet (CuCl)LaNb2O7

A quasi-two-dimensional S = 1/2 Heisenberg square-lattice antiferromagnet (CuCl)LaNb 2 O 7 is studied by specific heat and magnetic susceptibility measurements in external fields up to 14 T. The experimental results in low fields verify the absence of the order–disorder transition, as reported previously. By further application of magnetic fields, we obtain direct evidence for the phase transition, which can be interpreted as the Bose–Einstein condensation (BEC) of magnons. However, the critical field of 10 T significantly deviates from that estimated from the zero-field gap, indicating that, unlike known experimental examples, the one-magnon mode is not a primary source to drive the BEC.

The Villalbeto de la Peña meteorite fall: III. Bulk chemistry, porosity, magnetic properties, 57Fe Mössbauer spectroscopy, and Raman spectroscopy

Abstract— Detailed mineralogical and chemical studies and measurements of the magnetic properties and porosity of the Villalbeto de la Peña (L6) chondrite are reported. The measured abundances of 36 chemical elements are within the range observed for L6 chondrites for most elements, except for Pd and Os, which are particularly abundant in Villalbeto de la Peña. The specific magnetic susceptibility of the meteorite is 4.85 ± 0.05 (in 10−9m3kg−1) and the porosity is 4.7%. The JRS/JS (1.2 ± 0.2 × 10−3) and HC (3.3 × 10−4 T) values recorded are among the lowest ever reported for a chondrite. 57Fe Mössbauer spectroscopy of the whole rock indicates that the meteorite faced oxidizing conditions prior to fall. The Mössbauer spectrum of the metal fraction shows the presence of the only ferromagnetic phases kamacite and taenite. No tetrataenite is present, which is in total accordance to magnetic studies. Raman spectra yield compositional values for olivine (χMg ∼0.76), orthopyroxene (χMg ∼0.79), and clinopyroxene (χMg ∼0.49). Raman spectra of phosphate in shock veins indicates that Villalbeto de la Peña was not severely shock‐metamorphosed.