Y. Andoh

Magnetic Characteristics of Laves Phase RMn2 Compounds (R=Gd, Tb, Dy, Ho and Er)

Measurements of magnetization, susceptibility, thermal expansion and electrical resistivity have been carried out on the RMn 2 compounds with R=Gd, Tb, Dy, Ho and Er. Magnetization measurements were made on the single crystals for all the compounds. A simple ferrimagnetic structure is observed at 4.2 K for GdMn 2 , HoMn 2 and ErMn 2 , and an antiferromagnetic one in TbMn 2 . While, a canted ferrimagnetic structure appears at 4.2 K in DyMn 2 . The Mn moment deduced from saturation magnetization decreases rapidly from 1.6 µ B for GdMn 2 to 0.2 µ B for HoMn 2 with increasing the atomic number of rare earth in the C15 compounds. While, the Mn moment is almost zero in ErMn 2 with the C14 structure. Anomalous discontinuities in the thermal expansion and resistivity for GdMn 2 and TbMn 2 are observed at the magnetic transition temperature where Mn moments lose a long range ordering. It seems likely that the discontinuity is associated with the onset of the Mn moment.

Multistep magnetization of single crystal TbNiSn and DyNiSn in high fields

Abstract Magnetic and transport properties are reported on TbNiSn and DyNiSn single crystals with the orthorhombic TiNiSi-type structure. Thermal variation of the electrical resistivity and magnetic susceptibility indicates the existence of three successive magnetic transitions at T 1 = 6.0K, T 2 = 7.6K and T N = 18.5 K in TbNiSn and two magnetic transitions at T 1 = 5.4K and T N = 7.3 K in DyNiSn. Magnetization up to 15 T along the b -axis at 1.6 K exhibits a four-step metamagnetic transition for TbNiSn and a three-step one for DyNiSn. High-field magnetization curves for TbNiSn in fields up to 30 T at 1.4K show unexpected small jumps, which may suggest a switching of the magnetic axis.

Anisotropic hybridization in some cerium and uranium compounds with hexagonal ZrNiAl-type structure

Abstract Recent experimental results on the magnetic and transport properties of monocrystalline RTIn ( R  Ce and Nd ; T  Ni and Pd ) and UPdIn having the hexagonal ZrNiAl-type structure are presented and discussed in relation to the anisotropic hybridization effects. For CeTIn and UPdIn, the magnetic susceptibility X and electrical resistivity p along the α and c axes are significantly anisotropic and exhibit a remarkable contrast; X α > X c and p α ≈ 3 p c for CeNiIn, X c > X α and p α ≈ 1.5 p c for CePdIn, and X c > X α and p c > p α for UPdIn. On the monocrystalline NdTIn with stable 4f 3 electrons, the bare crystal electric field (CEF) parameters in the ZrNiAl-type crystal are deduced from magnetic measurements. From the comparison of the anisotropy in X calculated from the bare CEF parameters with the observed anisotropy, we argue that the anisotropic hybridization effect of the f electrons with ligand s, p and d electron states plays an important role in the anisotropy in the magnetic and transport properties of the cerium and actinide compounds.

Specific heats of PrNiSn and NdNiSn

Abstract The magnetic and specific heat experiments have been performed on the orthorhombic PrNiSn and NdNiSn single crystals to explore the ground states and the role of the crystalline electric field (CEF) in the compounds. Anisotropic behaviors in the susceptibility are well accounted for by the CEF effect for both the compounds. The data for PrNiSn do not show any magnetic ordering down to 0.9 K and suggest a nonmagnetic singlet ground state. NdNiSn exhibits an antiferromagnetic order below T N =2.8 K . A sharp jump (12 J / mol K ) in the specific heat near the TN confirms the bulk magnetic ordering.

Magnetic Properties of Laves Phase RRu2 Compounds (R=Gd, Tb, Dy, Ho and Er)

Magnetic studies have been performed on single crystals of the C-14 type Laves phase RRu 2 (R=Gd, Tb, Dy, Ho and Er) and the pseudo-binary (R 1- x Y x )Ru 2 (R=Tb, Dy, Ho and Er) compounds in the temperature rarxge from 4.2 K to 300 K. DyRu 2 shows a transition from cone structure to ferromagnetic one at 15 K and the other RRu 2 compounds exhibit ferromagnetism. The magntetization curves of the RRu 2 single crystals show their own characteristic behaviors dependent on the sort of R atoms. Lower moments for all RRu 2 compounds except GdRu 2 are observed at 4.2 K. The results are interpreted in terms of the single ion Hamiltonian including applied field, molecular field and crystal electric field (CEF) terms. From the analysis, the B n m ( n ≧4) terms were found to be dominant in this system. Tlne bi-quadratic exchange interaction seems to contribtate to magnetic properties in TbRu 2 and DyRu 2 .

Magnetization and Magnetocrystalline Anisotropy of Y1-xRxCo5(R=Pr and Sm) Compounds

The magnetizations of pseudo-binary Y 1- x R x Co 5 (R=Pr, Sm) single crystal compounds were measured at 4.2 K along the principal crystallographic axes. The magnetic moment per formula unit increases linearly with increasing x . The estimated values of the magnetic moments of Co atom in the compounds are independent of x and R elements. The magnetocrystalline anisotropy constants K 0 2 and K 0 4 were determined from the analysis of the hard magnetization curve. The values of K 0 2 and K 0 4 for Pr compound system increase quadratically with increasing x , and those of Sm compound system increase almost linearly with increasing x . We estimated the contribution of the single ion anisotropy and the two ion anisotropy for PrCo 5 and SmCo 5 compounds. For PrCo 5 compound, the two ion anisotropy constant was the same order of magnitude as the single ion one and of opposite sign to it, and for SmCo 5 compound, the former is negligibly smaller than the latter. The calculated value of the single ion anisotropy c...

Magnetic structure of TbNiSn single crystals

Abstract Measurements of magnetization and neutron diffraction have been performed on TbNiSn single crystals with an orthorhombic (Pnma) TiNiSi-type structure. Magnetic measurements indicate that this compound exhibits the four successive magnetic phase transitions at T1 = 2.0 K, T2 = 6.0 K, T3 = 7.6 K and TN = 18.5 K. There is little difference in neutron diffraction patterns between above and below T1. The magnetic structure is of a square-wave with Q = (0.600, 0.345, 0) for T 2 , Q = (0.665, 0.33, 0) for T 2 3 and of a sine-modulated type with Q = (0.685, 0.33, 0) for T3

Magnetic properties and magnetic anisotropy of RNiSn (R = Gd, Ho and Er) single crystals

Abstract Magnetic properties of RNiSn (R = Gd, Ho and Er) single crystals are reported. Antiferromagnet GdNiSn with T N = 11.0 K exhibits anisotropic magnetization process. Magnetic field of 125 kOe is required to overcome the exchange at 1.8 K. The saturation moment is in good agreement with the Gd 3+ free ion value 7.0 μ B . It is found that HoNiSn and ErNiSn order antiferromagnetically at T N = 3.0 and 4.0 K, respectively, and show strong anisotropy in susceptibility and magnetization.

Magnetic properties of NbFe2 single crystal

Abstract Magnetization measurements on nearly stoichiometric NbFe 2 single crystals have revealed the metamagnetic transition along the c -axis, which is consistent in supporting the previous NMR deduction that the magnetic ground state is antiferromagnetic. Anomalous and anisotropic temperature dependence of magnetic susceptibility has been observed: a remarkably difference in χ c -axis ( T ) and χ c -plane ( T ) below 200 K; the strong downward deviation from the Curie-Weiss law and the loss of anisotropy above 200 K.

Metamagnetic transitions in Nd7Ni3

Metamagnetic transitions in the intermetallic compound Nd 7 Ni 3 have been studied by measuring magnetization, magnetic susceptibility, magnetostriction as well as by neutron diffraction experiments under external magnetic fields up to 10 T. When the field is applied in the c -plane, there are three magnetic namely ferrimagnetic I, ferrimagnetic II and antiferromagnetic phases. In the ferrimagentic I phase, magnetic structure is conical with a basal plane helical component. In the ferrimagentic II phase, distorted helix structure is maintained. There are three metamagnetic transitions characterized by critical fields H C1 , H C2 and H C3 . Along the c -axis, a conical structure exists between T C and T N . Two metamagnetic transitions characterized by H C4 and H C5 were observed. The critical field from ferrimagnetic II and antiferromagentic phase has a maximum near 18 K. Magnetic field ( H )-temperature ( T ) phase diagrams for both field configurations are presented. A new magnetic or some another kind ...