The magnetic susceptibility of lutetium-hydrogen solid solution alloys from 2 to 300 K and a re-evaluation of the low temperature heat capacity results

The magnetic susceptibility, χ, of several lutetium-hydrogen solid solution alloys was measured between 2–300 K. Compositions varied from an electrotransport purified Lu (0.018 at% H) sample to 6.4 at% H alloy. Several samples exhibited large magnetic anisotropies, which complicated the analysis. The measured susceptibilities were compared to low temperature heat capacity results measured earlier on the same samples. It appears that pure Lu is a spin fluctuation material and the fluctuations are quickly degraded by impurities. While the variation of χ vs. composition is similar to that of γ (the electronic specific heat constant) vs. composition, the low temperature χ peaks near 3.0 at% H compared to 1.4 at% H for γ. This difference is thought to be due to hydrogen tunneling, which gives rise, in part, to a linear contribution to the heat capacity. Correcting for this brings the concentration dependence of γ in good agreement with the χ dependence of the hydrogen content.     

Intrinsic and extrinsic magnetic susceptibilities of some TCNQ complexes

The magnetic susceptibilities (χ) of quinolinium·(TCNQ)₂, N-methyl phenazinium·TCNQ and Li·TCNQ were measured from 2 to 300 K and are discussed in connection with the low-temperature specific heats (C) measured by other authors, χ is decomposed into three parts: χ_d the temperature-independent part, χ_c, Curie-Weiss type paramagnetism, and χ_p, the remainder. Correspondingly, C is composed of three terms, γT, H/T² and αT³. The electronic state of these substances is discussed in terms of each type of susceptibility.The model, on which the above separation of χ and C is based, defines two types of electrons: localized electrons associated with a magnetic moment and band electrons. Though this model is useful phenomenologically, it is shown that the analysis of χ on the basis of this model indicates less band electrons and more localized electrons or stronger magnetic interactions than does that of C.     

Structure-dependent magnetic susceptibility of sharp poly(ethylene oxide) fractions

Nine sharp fractions of poly(ethylene oxide) (PEO) glycol with number-average molar masses (M _n) in the range from 0.6 × 10³ to 20 × 10³ (PEO-0.6 to PEO-20) were characterized by magnetic susceptibility χ measured in the temperature interval 293 K to 378 K. In contrast to the liquidlike PEO-0.6 with temperature-invariant χ, the values of χ for each of the remaining solid samples, after the initial increase, exhibited two plateaus separated by a relatively narrow temperature interval of their second increase. The jumps of χ at lower and higher temperatures were attributed to a solid-state transition of unspecific nature and to the melting of the crystal fraction, respectively.

The temperature-invariant values of χ_n in the melt state above T _m pass through a minimum for the sample PEO-2.0 and then increase again with (M_n) to a limiting value χ_∞ = ?0.622 × 10^?6. It is concluded that a considerable contribution of the molar-mass-dependent “paramagnetism” χ_P = χ ^? χ_d (where χ_d is the diamagnetic contribution estimated by Kirkwood's equation) to the total magnetic susceptibility of PEO fractions reflects distortions of the spherical symmetry of the electron shells around chain atoms resulting from the discontinuous change of both inter- and intrachain interactions as the (M_n) increases through and above the critical crossover molar mass (M_cr ) = 2 × 10³.     

Crystal structure and magnetic susceptibility of (CuInSe<Subscript>2</Subscript>)<Subscript>1 − <Emphasis Type="Italic">x</Emphasis></Subscript>(2MnSe)<Subscript><Emphasis Type="Italic">x</Emphasis></Subscript>

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 × 10^t-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 Néel 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.     

Nuclear magnetic resonance and static magnetic susceptibility of AsF5 - intercalated graphite

NMR and static magnetic susceptibility (χ) measurements on stage 1 AsF₅ intercalated graphite (C₈AsF₅) are presented. The relaxation times, T_i and T₂, of the F¹⁹ nuclear magnetic resonance were measured over the temperature range 136K – 295K; χ was measured over the range 80K – 295K. The NMR results indicate a motionally narrowed line with gradual ordering of the intercalant as the temperature is decreased. The magnetic susceptibility is independent of temperature with no observable Curie law controbution. The absence of localized moment behavior for the intercalant is interpreted either in terms of chemical disproportionation of the AsF₅ to closed shell ions or in terms of the Anderson model of localized moments in metals.     

Magnetic and thermal properties of single-crystal NdFe<Subscript>3</Subscript>(BO<Subscript>3</Subscript>)<Subscript>4</Subscript>

The neodymium ferroborate NdFe₃(BO₃)₄ undergoes an antiferromagnetic transition at T _N = 30 K, which manifests itself as a λ-type anomaly in the temperature dependence of the specific heat C and as inflection points in the temperature dependences of the magnetic susceptibility χ measured at various directions of an applied magnetic field with respect to the crystallographic axes of the sample. Magnetic ordering occurs only in the subsystem of Fe³⁺ ions, whereas the subsystem of Nd³⁺ ions remains polarized by the magnetic field of the iron subsystem. A change in the population of the levels of the ground Kramers doublet of neodymium ions manifests itself as Schottky-type anomalies in the C(T) and χ(T) dependences at low temperatures. At low temperatures, the magnetic properties of single-crystal NdFe₃(BO₃)₄ are substantially anisotropic, which is determined by the anisotropic contribution of the rare-earth subsystem to the magnetization. The experimental data obtained are used to propose a model for the magnetic structure of NdFe₃(BO₃)₄.     

Magnetic, thermal and hyperfine behaviours of Tm3+ in TmPO4, YPO4 and LuPO4: a comparative study

Single crystals of thulium phosphates (TmPO₄) are grown and the principal magnetic susceptibility perpendicular to the symmetry axis ‘c’ of the crystal $$\left( {{\text{ $ \chi $ }}_ \bot } \right)$$ and the magnetic anisotropy $$\Delta {\text{ $ \chi $ }}\left( {{\text{ = $ \chi $ }}_\parallel - {\text{ $ \chi $ }}_ \bot } \right)$$ are measured in the temperature range 300–13.5 K and 300–80 K, respectively. Though $${\text{ $ \chi $ }}_ \bot $$ increases rapidly with the decrease of temperature, $${\text{ $ \chi $ }}_\parallel $$ increases very slowly with the lowering of temperature. The tetragonal crystal structure of TmPO₄ is similar to that of Tm³⁺ in YPO₄ and LuPO₄ and in all the cases the non-Kramers Tm³⁺ ion occupies a site of D_2d symmetry. Our observed magnetic data on TmPO₄ are analyzed using crystal field analysis where the Hamiltonian includes the atomic free ion and crystal field (one-electron) interaction term. The computed and measured paramagnetic susceptibilities of TmPO₄ agree very well in the temperature range of our study. The magnetic behaviours of Tm³⁺ in YPO₄ and LuPO₄ are also studied and the results are compared with that of TmPO₄. In all the cases the natures of thermal variations of average susceptibilities and magnetic anisotropies are mostly governed by the perpendicular susceptibilities as their values are higher and rapidly increase with the lowering of temperature compared to parallel susceptibilities. The computed nuclear quadruple splittings, electronic heat capacities of Tm³⁺ in three different hosts give some interesting results.     

Magnetic susceptibility of solid and liquid metals

Apparatus for the measurement of the magnetic susceptibilities of solid and liquid metals at temperatures up to 800°C is described. Prior to studying the susceptibilities of various metals through the melting point, the apparatus was tested by measuring the susceptibilities of tin and lead at room temperature, and the temperature dependences of susceptibility of several pure copper specimens enclosed in quartz bulbs. For copper, in the temperature range 20°C to 700°C,? _χ /?T = 1.9₂ × 10^?11 emu/g · deg C. This result is discussed in terms of the change of electronic susceptibility with volume expansion.     

Elastic-stress relaxation in compacted nanocrystalline CuO

The magnetic properties of two types of nanocrystalline antiferromagnetic CuO samples, namely, dense nanoceramics and loose powders, were studied. For nanomaterials with smaller particles, the magnetic susceptibility χ was shown to increase with a decrease in temperature T < T_N. The increase in χ in both series of samples is related to the disordering of Cu²⁺ spins at the surfaces of nanoparticles. The magnetic properties of nanopowders characterize the properties of isolated nanoparticles. In a dense nanoceramic, the size effect is compensated for by the interaction between nanoparticles. The magnetic properties of nanoceramics are determined by elastic stresses induced by an external action. Elastic-stress relaxation results in the recovery of magnetic order and decreases the magnetic susceptibility.     

Critical behaviour of a uniaxial ferromagnet,ErCl3·6H2O with predominant dipolar interactions

The parallel magnetic susceptibility χ of a uniaxial ferromagnet ErCl₃·6H₂O has been measured between 0.3 and 4.2K and specially near T_c = 0.353 K. The predominant contribution to the Curie-Weiss temperature is due to the dipolar interactions. χ is proportional to ?^?γ with $\text{? =}\text{T}\text{T}{}_{\mathrm{c}}\text{?1}$ in the range 10^?3 < ? < 5 × 10^?2. The γ value, γ = 1.01 ±0.03 is consistent with the theoretical prediction for a uniaxial dipolar ferromagnet.     

Magnetic properties of iron marcasite FeS2

The magnetic susceptibility, χ, of a natural single crystal of marcasite, FeS₂, has been measured between 300K down to 4K. At room temperature χ=0.3×10^?5 emu/g and it is temperature independent down to 10K. Below 10K it increases up to 1.3×10^?5 emu/g. It is concluded that iron in marcasite is in the Fe²⁺ low spin state, and that the 6d electrons occupy the t_2g ground state. Consequently iron in marcasite (FeS₂) is not magnetic in agreement with our Mössbauer spectra recorded at 4.2K in an external magnetic field up to 39.9 kOe. The small value of χ is explained in terms of contributions from ppm impurities. i.e., diamagnetism and Van Vleck paramagnetism.     

Superconductivity in Nb.95Ta.05Se3

We have measured the resistivity of NbSe₃ doped with 5% Ta from room temperature down to 0.5K and compared our results with similar measurements on pure NbSe₃. The pure sample remains normal to the lowest temperature (0.5K), whereas the doped sample has a sharp transition to the superconducting state with T_c = 1.5 ± 0.2 K. Measurements of the critical magnetic field indicate that the Ta doped samples are homogeneous, anisotropic three dimensional superconductors.     

The Langevin formula for describing the magnetization curve of a magnetic liquid

It has been shown that, at the initial stage of the magnetization curve, the magnetic susceptibility of magnetic liquid determined as χ = Mμ₀/B (M is the magnetization, B is the magnetic induction in a sample) obeys the Curie law, and the magnetic susceptibility determined as χ = M/H (H is the magnetic field intensity in a sample) obeys the Curie–Weiss law. Since the Curie law is a particular case of the Langevin dependence, it is assumed that an experimental magnetization curve is described by the Langevin formula with a Langevin parameter ξ = PB/kT, where P is the magnetic moment of a particle and T is the temperature. Experimental verification has shown that, at parameter ξ, the mean relative deviation between the values of M measured and calculated by the Langevin formula is 5%. This deviation can be accounted for by the influence of dispersion of the magnetic moments of nanoparticles.     

Linear and nonlinear AC magnetic susceptibilities in intercalation compound FexTiS2

The harmonic, second and third higher harmonic components of the induced voltage of a sample coil under application of a low-field ac magnetic field, with and without static field, have been measured in the spin-glass, cluster-glass, and ferromagnetic phases of the intercalation compound Fe_xTiS₂ over the temperature range 1.5-300 K. Using a phenomenological expression for the magnetization, we have obtained independently the relative magnitudes of the linear and nonlinear ac magnetic susceptibilities χ₀, χ₁ and χ₂ for each magnetic phase.     

Comparison between the magnetic susceptibilities of Pd1−xAgx and single phase PdHn

The rapid decrease of the isothermal magnetic susceptibility χ of single phase PdH_n with n ( = atomic ratio H/Pd) above the critical temperature T_c = 564 differs from that of the magnetically similar single phase system Pd_1−xAg_x (x: silver mole fraction) at the same temperature and at equal valence electron concentrations (n = x), i.e. χ (PdH_n)−χ(Pd_1−xAg_x) <0. By use of a semiphenomenological susceptibility ansatz related to the nonideal solution behaviour of H (Ag) in Pd the susceptibility difference is interpreted as an electronic excess effect.The analysis of the steep descent of the magnetic susceptibility also applies to the Pd-rich side of PdH_n in the subcritical temperature region (so-called α-phase) and can be supported by ¹⁰⁵Pd Knight shift data at 348 K.     

Peculiarities in the electron spectrum of superconducting laves phase ZrxHf1−xV2

Structurally unstable superconducting Laves phases Zr_xHf_1?xV₂ were investigated in the temperature range 4.2 – 300 K for temperature dependence of magnetic susceptibilities χ, resistivity ρ, and X-ray fluorescent emission 2K-spectra of vanadium. Anomalous dependences χ and ρ as compared to common metals was discovered below 150 K. This may be explained in terms of a phase transition of Peierl's type when the lattice instability results from the instability of the electron spectrum due to the dielectric slit that appears on flat parts of the Fermi surface. The presence of regions with localised electron density in the Laves phases on the low-energy side of the vanadium emission spectrum at low temperatures (T=10K) indicates an essential rebuilding in the electron spectrum of valence electrons.     

Influence of sample geometry on the magnetic-field induced metal-insulator transition in nHgCdTe

We report on measurements of the Hall-resistivity as a function of sample geometry in n-Hg_0.8Cd_0.2Te. The results demonstrate that the data measured with an nHgCdTe sample by Shayegan et al.¹ quite recently are a mere consequence of the sample geometry and do not represent the Hall resistivity. The magneto-transport properties of pure n-HgCdTe are not identical with those of n-InSb in strong magnetic fields and at low temperatures.     

Magnetic properties of the rare-earth diborodicarbides (RB2C2)

The magnetic susceptibility of RB₂C₂ has been measured in the temperature range of 3–300 K. Curie-Weiss fits to the susceptibilities led to effective moments in agreement with those expected for R³⁺ ions. The RB₂C₂ (R = Ce, Nd, Sm, Gd, Tb, Er, and Tm) compounds are antiferromagnetic. Metamagnetic transitions at low fields were observed for CeB₂C₂ and TbB₂C₂. The compounds, DyB₂C₂ and HoB₂C₂, are ferromagnets with complex magnetic structures. Praseodymium borocarbide becomes a Van Vleck paramagnet at low temperature. The magnetic ordering temperatures of these compounds are discussed in terms of their crystal structure and the RKKY theory.     

Magnetic and transport properties of Pr2Pt3Si5

We have investigated the magnetic and transport properties of a polycrystalline Pr₂Pt₃Si₅ sample through the dc and ac magnetic susceptibilities, electrical resistivity, and specific heat measurements. The Rietveld refinement of the powder X-ray diffraction data reveals that Pr₂Pt₃Si₅ crystallizes in the U₂Co₃Si₅-type orthorhombic structure (space group Ibam). Both the dc and ac magnetic susceptibility data measured at low fields exhibit sharp anomaly near 15 K. In contrast, the specific heat data exhibit only a broad anomaly implying no long range magnetic order down to 2 K. The broad Schottky-type anomaly in low temperature specific heat data is interpreted in terms of crystal electric field (CEF) effect, and a CEF-split singlet ground state is inferred. The absence of the long range order is attributed to the presence of nonmagnetic singlet ground state of the Pr³⁺ ion. The electrical resistivity data exhibit metallic behavior and are well described by the Bloch–Grüniesen–Mott relation.     

Surface magnetism of nanocrystalline copper monoxide

The effect of the surface on the magnetic susceptibility of nanopowders of the CuO semiconducting antiferromagnet was studied. Single-phase nanopowders with nanoparticles 15, 45, and 60 nm in size were prepared through copper vapor condensation in an argon environment, with subsequent oxidation of the copper. The temperature dependences of the magnetic susceptibility of the nanopowders differ qualitatively from the χ (T) relations for bulk samples. In the region 80≤T≤600 K, the magnetic susceptibility of nanopowders is inversely proportional to temperature and is described by the sum of contributions due to the bulk part of CuO and to the Cu²⁺ paramagnetic ions localized in surface layers. The paramagnetic contribution to the total susceptibility is shown to increase with decreasing particle size and sample density. A comparison of the χ (T) relations is made for nanopowders and for a dense CuO nanoceramic with grain size 5≤d≤100 nm prepared using the shock wave technique.