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Details of synthesis and characterization of sol-gel-produced CoFe²O4 nanoparticles embedded in the amorphous SiO² matrix are presented together with results of an extended magnetization study of these materials. The particle size was found to increase from 6 to 15 nm by varying the temperature of a subsequent annealing from 800 to 1100 °C. All samples exhibited superparamagnetic behavior with values of the blocking temperature TB increasing with the particle size. At temperatures above TB the magnetization curves follow the expected Langevin scaling of M vs H/T, which is consistent with the formation of the superparamagnetic state. For T

Two miniature uniaxial high-pressure CuBe cells have been designed for magnetic and neutron-diffraction studies of single crystals in a SQUID magnetometer and in a neutron diffractometer, respectively. Uniaxial elastic compression can be applied along or crosswise of the magnetic field direction or the diffractometer axis. Oriented single crystals are smoothly squeezed-up to a sample yield stress by a force of up to 20 kN produced by Bellville springs. The cell was successfully used for the study of huge anisotropy of magnetic interactions in the NdRhSn single crystal. [ABSTRACT FROM AUTHOR]

We report on the basic physical properties of a novel CeCo0.715Si2.285 compound, mainly its rich magnetic phase diagram. The compound crystallizes in the I-4m2 space group structure with extremely elongated unit cell (a = 4.12 Å, c = 32.84 Å). In a zero magnetic field it orders antiferromagnetically at TN = 10.5 K with another order-to-order transition at 9.5 K. Under application of a magnetic field along the c-axis it manifests numerous magnetic transitions in small fields (B < 500 mT), resembling the so-called "devil's staircase" systems. Above 1 T the magnetization is almost constant up to 14 T (maximum magnetic field applied within our study) but considerably reduced (0.3 μB/Ce) with respect to the free Ce3+ ion. After removing the applied field, however, the high field state remains unchanged to be removed in negative fields. The compound also exhibits strong hysteresis of magnetization with respect to varying temperature or magnetic field. For fields applied along the a-axis typical behavior for the hard axis in the material with uniaxial anisotropy is observed. [ABSTRACT FROM AUTHOR]

We report on synthesis and anisotropic physical properties of URhIn5. High quality single crystals were grown from In self-flux. The compound undergoes a second-order phase transition into an antiferromagnetic state at TN = 98 K. The transition is magnetic field independent up to 9 T. An increase of the resistivity ρ with j along the [100], [110] and [001] tetragonal axis indicates a spin-density-wave induced order with the gap opening first along the [001] direction. The magnetic susceptibility US χ= M/H exhibits a strong anisotropy. Above T = 200 K, US(T) follows the Curie-Weiss law with the effective moment of μeff = 3:71 μB/U and the Weiss temperatures of θ[100]p= -900 K and θ[100]p= -500 K for H k [100] and H k [001], respectively. The characteristic Kondo-like temperature for URhIn5 yields TK = 125 K. [ABSTRACT FROM AUTHOR]

Abstract: A PrRhSn single crystal has been grown and investigated with respect to magnetic behavior. The magnetization and specific heat were measured as functions of temperature (range 2–300K) and magnetic field (range 0–9T) applied along the main crystallographic axes. A strong uniaxial magnetocrystalline anisotropy was observed with the -axis as the easy magnetization direction. The transition temperature from paramagnetic to ferromagnetic state was determined to be . The specific heat data exhibit a Schottky anomaly just above . The anomaly is lifted to higher temperatures with an applied magnetic field along the -axis yielding a considerable magnetocaloric effect. [Copyright &y& Elsevier]

Abstract: We have investigated a single crystal of NdFe2Si2 by variety of macro- and microscopic experiments in wide range of temperatures and magnetic fields. The results confirmed antiferromagnetic ordering below the Néel temperature T N≈14K and uniaxial magnetocrystalline anisotropy with easy magnetization direction along the c-axis. Specific heat and dilatometry data exhibit an additional sharp anomaly below the T N, in particular at T t=13.1K, which was tentatively considered as a signature of an order–order magnetic phase transition. The neutron diffraction experiment, however, reveals no evidence of an order–order magnetic phase transition and confirms existence of only one magnetic structure up to the T N with propagation vector . The temperature dependence of the electrical resistivity shows only a single anomaly (at T N), consistently with neutron diffraction results. Furthermore, comprehensive neutron diffraction experiment is scheduled. [Copyright &y& Elsevier]

UNi2/3Rh1/3Al, a solid solution of UNiAl (Antiferromagnet (AF) with TN−19.3 K) and URhAl (Ferromagnet (F) with TC−27 K) exhibits no magnetic order due to a delicate balance of AF and F interactions. We report on a single-crystal susceptibility χ, magnetization M and resistivity ρ study. The huge uniaxial magnetic anisotropy typical for the parent compounds is preserved in UNi2/3Rh1/3Al. The χc vs. T (ρ vs. T) data exhibit a maximum (minimum) at 10 K. The Mc(B) curve at 1.6 K has a pronounced S-shape with an inflection around 12 T. The increase of ρ with decreasing T below 10 K is removed by magnetic fields. The low-T anomalies are attributed to proximity of magnetic order and AF correlations. The NFL features indicated earlier on polycrystals are not fully confirmed by single-crystal data. [Copyright &y& Elsevier]

Abstract: The magnetization (magnetic susceptibility), specific heat and electrical resistivity of a PrRhIn5 single crystal were studied. Van Vleck-type paramagnetic behavior and strong magnetocrystalline anisotropy were observed, which is attributed to a strong crystal-field effect on the Pr3+ ion. A crystal-field effect on the electrical resistivity was observed as well. We focused on the measurement of the specific heat down to low temperatures (down to 0.4K) in different magnetic fields. Indications of a field-induced transition to the quadrupolar ordered state below 0.4K were found in the specific-heat data in magnetic fields. First-principles calculations based on density functional theory of the electronic structure and crystal-field interaction were performed in order to better understand the experimental findings. [Copyright &y& Elsevier]

The experimental and theoretical study of magnetocaloric effect and magnetic relaxation of the powder sample of CsGd(MoO 4 ) 2 were performed. The large conventional magnetocaloric effect was found around 2 K with − Δ S max ≈ 26.5 J/(kg K) for B = 7 T. AC susceptibility measurement revealed multiple-time scale magnetic relaxation effects on different time scales. Slowest relaxation effect was attributed to the direct process with a bottleneck effect and two faster relaxation processes are effectively temperature independent, probably as a result of averaging in the powder sample. [ABSTRACT FROM AUTHOR]

Abstract: We report on magnetization, magnetic susceptibility, specific heat, electrical resistivity and thermal expansion measurements performed on a CeRhSn single crystal at temperatures between 2 and 300K and in magnetic fields up to 14T. No indication of magnetic ordering in low-temperature susceptibility, specific heat and resistivity was observed. Besides the maximum in the temperature dependence of resistivity for current along the a-axis no indication for the previously reported Ce-ion valence fluctuations was found in experimental data. In particular, the temperature dependence of susceptibility is monotonous and the magnetic specific heat above 20K is negligible. The linear thermal expansion is isotropic and has the character usual for normal metal. Based on these results we propose for CeRhSn an alternative scenario considering that the Ce 4f-electrons are itinerant. [Copyright &y& Elsevier]

Abstract: The lack of data obtained on single crystals of the REPdSn intermetallic compounds (RE =La, Pr, Nd) motivated us to grow single crystals of these compounds and to study intrinsic magnetic and related electronic and thermal properties of these materials with an emphasis on magnetocrystalline anisotropy. All the three compounds crystallize in the orthorhombic TiNiSi-type crystal structure. The results of specific heat, magnetization and resistivity measurements have revealed that LaPdSn is a paramagnet at temperatures down to 2K, PrPdSn and NdPdSn order antiferromagnetically below T N =4.2(1) and 3.4(1) K, respectively, and exhibit considerable magnetocrystalline anisotropy. The latter compound undergoes an order-to-order phase transition at 1.9(3)K. At sufficiently high temperatures the susceptibility of the Pr- and Nd-compounds follows a Curie–Weiss law with the effective magnetic moment almost identical in all the three principal crystallographic directions to the value expected for the corresponding free RE 3+ ion. The values of the paramagnetic Curie temperature manifest the anisotropy of the susceptibility in paramagnetic state, which is particularly pronounced for PrPdSn. As temperature decreases the susceptibility exhibits anisotropic departure from the Curie–Weiss behavior as a consequence of the crystal field (CF) influence on the RE ions. The involvement of the crystal field in the magnetism of the RE ions is also reflected in the Schottky contribution to the specific heat which reflects the splitting of the CF energy levels and the reduced values of the RE ordered magnetic moments due to the unpopulated higher-energy CF energy levels at low temperatures. Interesting features of magnetism in PrPdSn and NdPdSn are reflected also in the electrical resistivity and magnetoresistivity. For closer understanding of magnetism in the studied REPdSn compounds we have also performed first principles electronic structure calculations. We present the calculated density of states (DOS) of REPdSn compounds and we also compare the obtained experimental results with the theoretical predictions from the calculated electronic structure. [Copyright &y& Elsevier]

Abstract: We have grown a single crystal of PrRhSn, analyzed the structure by X-ray diffraction methods and measured the specific heat, ac susceptibility, magnetization, and electrical resistivity as functions of temperature and magnetic field. Also we have calculated the electronic structure of this compound by ab initio methods. Ferromagnetism below T C =2.9K characterized by strong uniaxial anisotropy (an anisotropy field ∼65T) has been confirmed. Pronounced crystal field (CF) effects were observed on the temperature dependences of the magnetic susceptibility, electrical resistivity and specific heat. The calculations revealed that besides the stable Pr magnetic moment owing to the localized 4f-electrons a small magnetic moment of at most 0.2μ B is induced at the Rh site (and 0.1μ B at the Sn site) due to the polarized Rh 4d-electron states (Sn 5p-states) hybridizing with the Pr 5d-electron states, i.e. the Rh and Sn moments play some role in the total balance of the magnetic moments in this compound. This result is in agreement with the experimentally determined saturated magnetic moment of PrRhSn, which is about 0.3μ B larger than the ordered moment value expected for the Pr3+ free ion. [Copyright &y& Elsevier]

We present the study of the Kondo antiferromagnet CePtSn, whose magnetic properties at T>TN can be explained by a strong anisotropy of the crystal-field (CF) potential on the Ce sites, which have an orthorhombic point-group symmetry. Applying a microscopic model with parameters deduced from magnetization and inelastic neutron scattering (INS) data, we predict a strong magnetic dipole moment parallel to the a-axis in the ground state. The dramatically increased count rate at the upgraded ILL three-axis spectrometer IN20 permits now to use the polarized beam even with a small single crystal sample (0.2 cm3) to separate the CF signal from phonon background and to employ the XYZ polarization analysis to confirm directly this previously deduced anisotropy of the local CF Hamiltonian. [Copyright &y& Elsevier]

Abstract: CeCoGe is an antiferromagnet with the Ce magnetic moments lying in the basal plane of the tetragonal lattice. A metamagnetic transition with a magnetization jump of 0.5 μ B is observed at B c=8.5T (at 2K) applied along the a-axis. With increasing temperature, the B c value passes through a minimum in the vicinity of T N and then increases up to at least 10K, i.e. above T N=5.5K. In a field along the c-axis, a broad S-shape magnetization curve is observed only at temperatures below T N. The anisotropic behavior persists above T N as well. [Copyright &y& Elsevier]

Abstract: A GdNi single crystal has been prepared by the Czochralski method and studied by measuring the magnetization, electrical resistivity and thermal expansion. The ferromagnetic ordering below T C=69K has been confirmed. The saturated magnetization at 2K was found to be identical (7.2 μ B/f.u.) along all the three principal crystallographic directions. This result is in agreement with theoretical calculations, which yield magnetic moment of 7.0 μ B/f.u. for Gd3+ ion and 0.18 μ B/f.u. for conduction electrons with magnetic moment of the same direction as the Gd moment. An anomalous spontaneous magnetostriction is dominating the thermal expansion behavior below T C. In particular, we have observed a large contraction in the c-direction and a smaller expansion in the a and b directions (nearly identical). The unit cell volume expands below T C (ΔV/V=8×10−4). The observed anisotropy of the magnetostriction in GdNi is attributed to anisotropic magnetoelastic coupling. [Copyright &y& Elsevier]