High-field Magnetic Susceptibility Research Articles

Frustrated magnetism in the tetragonal CoSe analog of superconducting FeSe

Recently synthesized metastable tetragonal CoSe, isostructural to the FeSe superconductor, offers a new avenue for investigating systems in close proximity to the iron-based superconductors. We present magnetic and transport property measurements on powders and single crystals of CoSe. High field magnetic susceptibility measurements indicate a suppression of the previously reported 10 K ferromagnetic transition with the magnetic susceptibility, exhibiting time dependence below the proposed transition. Dynamic scaling analysis of the time dependence yields a critical relaxation time of ${\ensuremath{\tau}}^{*}=0.064\ifmmode\pm\else\textpm\fi{}0.008$ s which in turn yields activation energy ${E}_{a}^{*}=14.84\ifmmode\pm\else\textpm\fi{}0.59$ K and an ideal glass temperature ${T}_{0}^{*}=8.91\ifmmode\pm\else\textpm\fi{}0.09$ K from Vogel-Fulcher analysis. No transition is observed in resistivity and specific heat measurements, but both measurements indicate that CoSe is metallic. These results are interpreted on the basis of CoSe exhibiting frustrated magnetic ordering arising from competing magnetic interactions. Arrott analysis of single crystal magnetic susceptibility has indicated the transition temperature occurs in close proximity to previous reports and that the magnetic moment lies solely in the $ab$ plane. The results have implications for understanding the relationship between magnetism and transport properties in the iron chalcogenide superconductors.

Enhanced magnetization of the Marlboro Clay as a product of soil pyrogenesis at the Paleocene–Eocene boundary?

The kaolinite-rich Marlboro Clay was deposited on the inner shelf in the Salisbury Embayment of the U.S. Atlantic margin at the onset of the carbon isotope excursion marking the 56 Ma Paleocene–Eocene boundary and is characterized by an anomalously high concentration of magnetic nanoparticles of enigmatic origin that give rise to notably intense bulk magnetization. Recent studies point to a magnetic assemblage that is dominated by single-domain magnetite particles that tend to be isolated rather than arranged in chains, the most distinguishing feature of magnetotactic bacteria fossils. On the other hand, it is very unlikely that the nanoparticles can be condensates of an impact plume given the meter-scale thickness of the Marlboro Clay. We obtained new data from a landward proximal site at Wilson Lake on the New Jersey Coastal Plain and find that the abrupt increase in magnetite nanoparticles is virtually coincident stratigraphically with the recently reported impact spherule layer at the base of the Marlboro Clay in the same core. Yet the high field magnetic susceptibility, a measure of total iron concentration, and strontium isotope values on bulk sediment, an indicator of sediment weathering provenance, are not different in the Marlboro Clay from the immediately underlying Vincentown Formation. We suggest that the distinctive magnetic properties of the Marlboro Clay originated from pyromagnetic soil enhancement by widespread wildfires on the adjoining drainage area. The pyrogenetic products were soon washed from the denuded landscape and rapidly deposited as mud-waves across the shelf, becoming the Marlboro Clay. A few percent of incinerated biomass ends up as calcite known as wood ash stone and can inherit its light carbon isotope composition. Disseminated wood ash stone entrained in the Marlboro Clay could contribute to the landward increase in amplitude of the carbon isotope excursion in bulk carbonate data. A plausible trigger for the initial conflagration is a fireball from the impact of a sizable extraterrestrial object at moderate range.

Phase equilibria and magnetic properties of Heusler-type ordered phases in the Co–Mn–Ga ternary system

Phase equilibria at 800, 900 and 1000°C, as well as order–disorder and magnetic transitions of Heusler-type ordered phase were investigated in the Co–Mn–Ga ternary system. The β phase with bcc structure including the Heusler-type ordered phase exists in a wide composition range of the ternary system. It was confirmed by STEM–HAADF observation that the crystal structure of the Heusler-type ordered alloy Mn2CoGa is L21b-type Fm3¯m (i.e., (Mn,Co)2MnGa), but not inverse-Heusler (Hg2CuTi) type F4¯3m. The L21/B2 order–disorder transition temperature shows a maximum at the stoichiometric composition of Co2MnGa and the Curie temperature of the L21 phase decreases with increasing Ga content. Magnetic moments converted from magnetization curves at 4.2K for CoxMn(76−x)Ga24 alloys well follow the generalized Slater–Pauling rule in the composition of 25⩽x⩽50, and magnetization curves indicate very small high-field magnetic susceptibility.

Absolute calibration of low- and high-field magnetic susceptibilities using rare earth oxides

Low- or high-field magnetic susceptibility measurements have been routinely utilized in or even beyond paleomagnetism and environmental magnetism. Susceptibility meters, such as Bartington or Kappabridge, are now commercially available and have enabled us to measure a variety of samples readily. However, interlaboratory or interinstrument calibration is not yet faithfully performed on absolute or even relative scales. The reason is that no standard material is generally accepted for susceptibility calibration. Gadolinium or other rare earth oxides are considered as ideal standard materials because of the high chemical stability. We defined reference susceptibility values for all available paramagnetic rare earth oxides after carefully examining the Landolt-Bornstein database and selected four compounds Nd2O3, Gd2O3, Dy2O3 and Er2O3 as standard materials. We carried out calibration measurements using Bartington and Kappabridge susceptibility meters, a Magnetic Property Measurement System (Quantum Design) and a Vibrating Sample Magnetometer (Princeton Measurements Corporation). Linear relationships between measured and reference values were observed for all the instruments. In some cases, however, measured values deviated significantly from expected values, suggesting that calibration is indeed necessary. If any instrument is calibrated with these rare earth oxides, we can reliably compare absolute susceptibility values measured with any kind of instrument in different laboratories.

Magnetic State of Y<sub>3</sub>Fe<sub>5-X</sub>Sc<sub>x</sub>O<sub>12</sub> Garnets

Ferrogarnets of the system {Y3}[Fe2-xScx](Fe3)O12 were investigated by neutron diffraction and magnetic methods. Parameters of crystal structure were refined. It was found that deviations from a collinear ferrimagnetic structure emerged at x ~ 0.7. At high concentrations of Sc a growth of the high-field magnetic susceptibility and an abnormal temperature dependences of dynamic susceptibility typical of local angular spin structures were revealed. The fracture temperatures for the local angular structures were determined.

Anisotropic magnetic susceptibility record of the kinematics of the Boltaña Anticline (Southern Pyrenees)

AbstractAnisotropic magnetic susceptibility (AMS) analysis of 1454 samples evenly distributed along an 1800 m section in the South Pyrenean Zone is presented. The sampled rocks are pre‐ and syn‐tectonic limestones, marls and sandstones of Ypresian‐Lutetian age. They are weakly deformed rocks sampled from both limbs of the N–S trending Boltaña Anticline (oblique to the WNW–ESE main Pyrenean trend). Rock magnetism analyses, including low temperature and high field magnetic susceptibility measurements confirm a dominant paramagnetic signal and hence allow the interpretation of AMS in terms of preferred rock fabric or finite strain orientation. Therefore, this study was focused on obtaining an independent kinematic information from a vast set of AMS data from particular structural positions. The three directional maxima for the maximum axis of the magnetic ellipsoid (KMAX, magnetic lineation) can be tentatively related to major tectonic events in the Central Pyrenees. A first stage (recording a N–S magnetic lineation) is related to an oblique ramp of the Cotiella Thrust, emplaced during Ypresian times. A pseudo‐progressive variation turns into a second stage (linked to a NW–SE KMAX orientation maximum) that can be related to Pyrenean compression. Both stages witness a far‐field imprint of active structures on the foreland sediments. Once the Boltaña Anticline was nucleated (during the Lutetian), a predominant, more constant NW–SE trend is observed, this near‐field magnetic fabric being the only lineation imprinted in the rocks. A final stage arrived in the course of vertical axis rotation during the Late Lutetian‐Bartonian. This latest event was responsible for the present configuration of the Boltaña Anticline (N–S). Copyright © 2010 John Wiley & Sons, Ltd.

Hyperfine coupling constant for 59Co estimated from a high-field susceptibility and high-field NMR shift in ferromagnetic Co2TiGa and Co2VGa

The hyperfine coupling constant for 59Co in the ferromagnetic state of a Heusler alloy Co2TiGa in the high-field range has been estimated to be 170 kOe per 1 μB of the moment of cobalt atom from the high-field magnetic susceptibility of 2.3 × 10−6 emu/gOe measured at 5 K in a field range from 20 to 70 kOe and a reported positive high-field NMR shift of +0.83 percent. The value of the hyperfine coupling constant has been found to be even larger in the case of Co2VGa. These features suggest that the positive hyperfine field at Co nucleus in the Co-based Heusler alloys is due to conduction electron polarization rather than a transferred hyperfine field.

Effect of Co or Mn addition on the soft magnetic properties of amorphous Fe 89−xZr 11B x ( x=5, 10) alloy ribbons

The temperature and field dependent magnetic properties of melt-spun amorphous Fe 89− x − y Zr 11B x (Co,Mn) y ( x=5, 10 and 0≤ y≤10) alloys in the temperature range 5–1200 K are reported. The Curie temperature and saturation magnetization at room temperature increase (decrease) almost linearly with Co (Mn) addition. With increasing Co concentration, the room temperature coercivity increases at the rate of 2.26 (0.28) A/m per at% for the x=5 (10) samples. The high-field magnetic susceptibility and local magnetic anisotropy decrease (increases) rapidly with increasing Co (Mn) concentration. The thermomagnetic curves show a marked increase in magnetization above 850 K corresponding to the crystallization of α-FeCo (α-Fe) phase in samples containing Co (Mn). The Curie temperature of the crystalline phase increases (remains same) with increasing Co (Mn) concentration with the formation of α-FeCo (α-Fe). Addition of Co up to 10 at% in Fe–Zr–B improves the room temperature saturation magnetization from 0.56 to 1.2 T, and Curie temperature from 315 to 476 K. Also, the coercivity increases with Co addition from 1.27 to 23.88 A/m for x=5 and from 7.64 to 10.35 A/m for x=10 alloy. The non-collinear spin structures that characterize Fe rich Fe–Zr–B amorphous alloys have been used to describe the observed results.

High-Field EPR and Magnetic Susceptibility Studies on Binuclear and Tetranuclear Copper Trifluoroacetate Complexes. X-ray Structure Determination of Three Tetranuclear Quinoline Adducts of Copper(II) Trifluoroacetate

Magnetic properties and high-field EPR spectra of three previously unknown tetranuclear quinoline adducts of copper(II) trifluoroacetate were studied, and their X-ray structures were determined. Two green complexes containing a mu(4)-oxo bridge, Cu(4)O(CF(3)COO)(6)(quin)(4) x (C(6)H(5)CH(3))(0.6) (orthorhombic, Pbca, a = 15.278(3), b = 23.227(5), c = 34.895(7) A) and Cu(4)O(CF(3)COO)(6)(quin)(4) x (C(6)H(6))(0.8) (monoclinic, P2/c, a = 21.933(4), b = 11.176(2), c = 23.927(5) A, beta = 97.41(3) degrees) are ferromagnetic, whereas the blue complex [Cu(4)(OH)(2)(CF(3)COO)(8)(quin)(2)](2-)(quinH(+))(2) (monoclinic, a = 21.933(4), b = 11.176(2), c = 23.927(5) A, beta = 97.41(3) degrees), formed in humid air from the solid dimeric [Cu(CF(3)COO)(2) x (quin)](2), is antiferromagnetic, as is the tetranuclear blue product formed in humid air of the mu(4)-oxo tetramers. High-field EPR spectra allowed determination of the spin Hamiltonian parameters for the spin quintet state (S = 2) in the ferromagnetic complexes, which facilitated accurate interpretation of their magnetic susceptibility data. "Broken symmetry" DFT calculations were performed to estimate the exchange integrals in all three tetranuclear complexes, showing surprisingly good agreement with experimental results. Negative sign of the zero-field splitting parameter D in two binuclear complexes, [Cu(CF(3)COO)(2) x CH(3)CN](2) and [Cu(CF(3)COO)(2) x (quin)](2), was found from single-crystal high-field EPR spectra, confirming recent results for nonhalogenated dimeric copper carboxylates.

The magnetic stratification of layered mafic intrusions: Natural examples and numerical models

Mafic–ultramafic intrusions commonly display a prominent petrographic and geochemical layering attributed to differentiation in a magma chamber. This layering occurs at scales from several hundreds of meters in some large intrusions, down to scales of a few millimeters. Layering-forming processes are numerous and include, both internal processes, such as crystal settling, double diffusive convection, flow segregation and compaction, and external processes such as magma-recharge, -extraction or -mixing. Mafic magma chambers may operate as a closed system or as an open system. Several recent investigations have been conducted on borehole cores through the Insizwa sill (South Africa), the Great Dyke (Zimbabwe), and the Bushveld Complex (South Africa). We present an overview of magnetic results on these intrusions. The magnetic properties of mafic rocks are dominated by the presence of magnetite in most layers. Pyrrhotite, the only ferrimagnetic sulfide, is generally restricted to sulfide-rich reefs (Merensky, J-M, Böhmke) or to massive sulfide deposits at the base of the intrusion. All intrusions display distinct variations of their magnetic properties (anisotropy of magnetic susceptibility, magnetic remanence, magnetic saturation, high field magnetic susceptibility) across the layering. The significance of these magnetic zones varies depending on the nature of variations from zone to zone. For example, a drop in magnetic susceptibility does not necessarily correspond to a new magma batch, unless it is also associated with a change in magnetic anisotropy parameters. In the studied cases, all open systems, the magnetic susceptibility and the total iron content (estimated from high field measurements) increase towards the top of these intrusions suggesting a general pattern of iron enrichment. A numerical petrologic model for a tholeiitic magma predicts magnetic susceptibility variations across a statically differentiated, closed system intrusion (no convection). The effects of sequential magma recharge and discrete magma extraction are investigated from the magnetic properties point of view. Conversely, these models can be used to interpret the magnetic stratification pattern in natural examples and test for its possible causes.

Formation and evolution of magnetic nanoparticles in borate glass simultaneously doped with Fe and Mn oxides

Evolution of the phase state of paramagnetic additions at various stages of synthesis and subsequent thermal treatment of glasses of the system Al2O3–K2O–B2O3 simultaneously doped with Fe2O3 and MnO is studied by means of a combination of experimental techniques: Faraday rotation (FR), electron magnetic resonance (EMR), transmission electron microscopy (TEM), Mössbauer spectroscopy, and magnetic measurements. Both FR and EMR show that magnetically ordered clusters occur already at the first stage of the glass preparation. In particular, for the ratio of the Fe and Mn oxides in the charge close to 3:2, fine magnetic nanoparticles are formed with characteristics similar to those of manganese ferrite. By computer simulating the EMR spectra at variable temperatures, a superparamagnetic nature of these nanoparticles is confirmed and their mean diameter is estimated as approximately 3.2 nm. In the thermally treated glasses larger magnetic nanoparticles are formed, giving rise to FR spectra, characteristic of magnetically ordered systems, and the EMR spectra different from those in as-prepared glasses but also showing superparamagnetic narrowing. The Mössbauer spectroscopy corroborates the manganese ferrite structure of the nanoparticles and indicates their coexistence in the ferrimagnetic and superparamagnetic states. The TEM shows the presence of polydisperse nanoparticles on the background of the glass matrix, and electron diffraction of a selected region containing larger particles indicates a crystal structure close to that of MnFe2O4. Energy-dispersive atomic x-ray spectra confirm that the major part of Fe and Mn introduced to the glass composition is gathered in the particles, with the concentration ratio close to 2:1, characteristic of bulk MnFe2O4. Magnetic hysteresis loops of samples subjected to an additional thermal treatment demonstrate a strong increase in the coercive force, remnant magnetization, and high-field magnetic susceptibility with temperature decrease. The consistent results obtained using various techniques demonstrate that the formation of nanoparticles with characteristics close to those of MnFe2O4 confers to these glasses magnetic and magneto-optical properties typical of substances possessing magnetic order.

Chapter 9 - Half-Metallic Systems: Complete Asymmetry in Spin Transport

There are systems with metallic spin-up and spin-down electrons, that is, both spins contribute to the Fermi level density of state (and transport). For highly spin polarized systems, it can be envisioned having a situation where one spin channel shows metallicity while the other spins are insulating. Such materials, where tunneling currents show 100% spin polarization when used in tunneling devices, have been found and are called half-metals. Half-metals have unusual electronic properties. For one type of spin, the half-metal looks metallic with a well defined Fermi surface. For the opposite spin, there is a gap in the state density. In half-metals, there is a clear gap in the density of states corresponding to one type of spin. These half-metals do conduct electricity but do not show a high field magnetic susceptibility. All half-metals contain more than one element with most of them being oxides or Heusler type alloys. In real half-metals, conduction is carried out almost entirely by one spin channel. There is no clear experimental signal to identify half-metals. If the minority (or majority) gap is a true gap (with zero total density of states) then it is possible to conclude that the majority and minority counts of spin have to be integers per unit cell. The band gap for one spin type is the defining feature of these materials, therefore, the chapter are the three different categories of gaps—covalent band gaps, charge-transfer gaps, and d-d band gaps. Half-metals in different categories listed above respond differently to external parameters such as pressure because of different electronic structures that give rise to half-metallicity in these three categories. The chapter discusses half Heusler alloys: NiMnSb and PtMnSb, full Heusler alloys: Co 2 MnSi, Co 2 MnGe, Co 2 Cr 1-x Fe x Al, chromium dioxide, perovskites and double-perovskites, and multilayers of zincblende half-metals with semiconductors.

Heisenberg model of an {Fe8}-cubane cluster

An analysis of the measured magnetic susceptibility of the recently synthesized magnetic molecule Fe8-cubane Fe 8 O4sao8py4 leads to a detailed proposal based on an isotropic Heisenberg model for the interactions between the eight Fe III ions. In the theoretical model, the magnetic ions are situated on the vertices of a cube with one exchange constant linking nearest neighbors and a second exchange constant appearing as a single diagonal across each of the six faces of the cube linking four of the eight ions on alternate sites. Excellent agreement between the experimental and theoretical susceptibility data is achieved, thereby providing estimates for the numerical values of the two exchange constants. Independent tests of the theoretical model are proposed in terms of inelastic neutron scattering and high-field magnetic susceptibility measurements at low temperatures that would probe the predicted low-lying magnetic energy levels of the system.

Magnetic record associated with tree ring density: Possible climate proxy

A magnetic signature of tree rings was tested as a potential paleo-climatic indicator. We examined wood from sequoia tree, located in Mountain Home State Forest, California, whose tree ring record spans over the period 600 – 1700 A.D. We measured low and high-field magnetic susceptibility, the natural remanent magnetization (NRM), saturation isothermal remanent magnetization (SIRM), and stability against thermal and alternating field (AF) demagnetization. Magnetic investigation of the 200 mm long sequoia material suggests that magnetic efficiency of natural remanence may be a sensitive paleoclimate indicator because it is substantially higher (in average >1%) during the Medieval Warm Epoch (700–1300 A.D.) than during the Little Ice Age (1300–1850 A.D.) where it is <1%. Diamagnetic behavior has been noted to be prevalent in regions with higher tree ring density. The mineralogical nature of the remanence carrier was not directly detected but maghemite is suggested due to low coercivity and absence of Verwey transition. Tree ring density, along with the wood's magnetic remanence efficiency, records the Little Ice Age (LIA) well documented in Europe. Such a record suggests that the European LIA was a global phenomenon. Magnetic analysis of the thermal stability reveals the blocking temperatures near 200 degree C. This phenomenon suggests that the remanent component in this tree may be thermal in origin and was controlled by local thermal condition.

Valence and Na content dependences of superconductivity inNaxCoO2∙yH2O

In order to acquire knowledge of the general superconducting phase diagram of sodium cobalt oxyhydrate, various samples with relatively large amounts of ${\mathrm{Na}}^{+}$ ions were synthesized by a modified soft-chemical process in which a NaOH aqueous solution was added in the final step of the procedure. From these samples, a superconducting phase diagram was determined for a section of cobalt valence of $\ensuremath{\sim}+3.48$, which was compared with a previously obtained one of $\ensuremath{\sim}+3.40$. In addition, it was proven that the superconductivity was significantly affected by the isovalent exchange of ${\mathrm{Na}}^{+}$ and ${\mathrm{H}}_{3}{\mathrm{O}}^{+}$, implying that the ${e}_{g}^{\ensuremath{'}}$ bands play an important role in the superconductivity. Furthermore, the high-field magnetic susceptibility measurements for one sample indicated an upper critical field much higher than $8\phantom{\rule{0.3em}{0ex}}\mathrm{T}$.

High-field magnetic susceptibility ( χHF) as a proxy of biogenic sedimentation along the Antarctic Peninsula

High-field mass-normalized magnetic susceptibility ( χ HF) is presented as a proxy for biogenic sedimentation in glacimarine sediment from the western Antarctic Peninsula. χ HF is measured at field strengths that exceed the saturation field of ferrimagnetic minerals. These measurement conditions exclude the contributions of ferrimagnetic iron oxides that dominate low-field volume-normalized susceptibility ( k) measurements. Therefore, χ HF allows for closer examination of paramagnetic and diamagnetic minerals, the latter of which includes biogenic silica and biogenic calcite. In sedimentary sequences from the western Antarctic Peninsula, the main processes affecting the abundance of diamagnetic material in sediment is biological productivity and the subsequent flux of biogenic silica to the seafloor. χ HF profiles were measured on two biosiliceous sediment cores from the western Antarctic Peninsula. Comparisons with quantitative biogenic silica measurements indicate that χ HF tracks % opaline silica very well, and reveals the presence of century-scale cycles in sediment composition in intervals where k appears featureless. χ HF is limited as a quantitative measure of biogenic sediment flux, since terrigenous paramagnetic and diamagnetic minerals also contribute to the measurement. The interpretation of χ HF can also be complicated by the presence of unsaturated high-coercivity minerals such as hematite and goethite, or by the presence of ultra-fine superparamagnetic (SP) particles. However, in sediment sequences where the condition of saturation is met, χ HF is very well suited for the rapid identification of temporal trends in biogenic sedimentation.

Electron delocalisation in a trinuclear copper(ii) complex: high-field EPR characterization and magnetic properties of Na3[Cu3(mal)3(H2O)]·8H2O

The complex Na3[Cu3(mal)3(H2O)] x 8H2O was obtained from evaporation of an aqueous solution containing Cu(OAc)2, malic acid (HO2CCH2CHOHCO2H) and NaOH and was characterised by X-ray diffraction on single crystal, X-band and high-field EPR spectroscopy (HF-EPR) and magnetic susceptibility measurements. The trinuclear complex [Cu3(mal)3(H2O)]3- is trapped in a three-dimensional network with sodium cations. The three copper atoms are connected by alkoxo bridges and form an almost isosceles triangle with Cu...Cu distances of 3.076(1), 3.504(1) and 3.513(1) A. Two of the copper ions are also bridged by an extra aquo ligand. EPR spectroscopy combined with magnetic susceptibility measurements provide a powerful tool to resolve the electronic structure of the complex. The overall magnetic behaviour corresponds to an antiferromagnetically coupled triangular system. The 285 GHz-EPR spectrum (g = 2; 10.18 T) is characteristic of a spin state S = 1/2, with a rhombic anisotropy of [g]. This rhombic pattern allows us to propose that the electronic spin density is delocalised on the three copper ions.

Magnetization and magnetic susceptibility of jadeite

We have studied the high-field magnetization (up to 14.5 T) and magnetic susceptibility in the temperature range 1.7 - 420 K of two samples of jadeite (NaAlSi2O6), white and green, containing transition metal ions and originating from Burma (now Myanmar). It appears that the high-temperature susceptibility data obey the Curie-Weiss law indicating the onset of the antiferromagnetic interaction between the magnetic ions. This interaction is also seen in the high-field magnetization data which are well described by the phenomenological cluster model. As a result of our analysis, we have identified the Fe3+ ions as the dominant ones in the studied jadeites and we have determined the molar concentration of these ions (0.8% in white- and 2.5% in green jadeite) as well as the diamagnetic susceptibility of the jadeite matrix (-3.8 × 10-7 emu/g).

Magnetic properties of multiwall nanotubes

The diamagnetic susceptibility of multiwall carbon nanotubes is studied as function of magnetic field and temperature. Both the low-field and the low-temperature susceptibility reveal a definite paramagnetic upturn in qualitative agreement with the Aharonov–Bohm effect. Analysis of the high-field magnetic susceptibility in terms of the orbital diamagnetism of quasi-two-dimensional graphite implies hole-doping and supports further the intrinsically divergent paramagnetic contribution of small metallic nanotubes.

A new energy scale at low temperatures in YbAl 3

We observed high magnetic field de Haas–van Alphen signals up to 57 T at low temperatures down to 0.5 K in the intermediate valence compound YbAl 3. High-field magnetization and magnetic susceptibility measurements imply that new electronic states in YbAl 3 are created with an energy scale of 40 K . In the 〈1 1 1〉 direction, the effective masses, which are 13.5 m 0 for the α-branch and 23.9 m 0 for the β-branch at low magnetic fields (<40 T) , are strongly reduced to 5.25 m 0 for both branches at high magnetic fields (>40 T) .