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Magnetic studies were performed on PrPd2Si2 single crystals which crystallize in the tetragonal ThCr2Si2-type structure. The temperature dependence of the magnetic susceptibility indicates that the compound orders antiferromagnetically at temperatures below T N = 3.2 K. The transition was confirmed by specific heat measurements. Magnetization measurements at fields up to 18 T show that the easy magnetization direction is the [100] direction in the basal plane. In the magnetization process, five or four metamagnetic transitions appear; the process is a five (four)-step metamagnetic one. The [110] magnetization process is a three-step one. A strong magnetic anisotropy between the [100] and [110] directions is observed within the basal plane for high magnetic fields. Along the hard magnetization direction of the c-axis, a metamagnetic transition appears. The B [100] − T phase diagram was constructed. A magnetic anisotropy between the [100] and [001] directions is also strong. These behaviors are discussed based on an analysis of crystalline field effects.

Measurements of the magnetization and the specific heat were performed on a PrRh2 single crystal. A strong magnetic anisotropy with the easy magnetization direction of the c-axis is observed. Four anomalies appear in the temperature dependence of magnetic susceptibility along the c-axis; a cusp at TN=52 K, a high peak at T3=38 K, a shoulder at T2=33 K and a small peak at T1=4 K are observed, indicating magnetic transitions. The specific heat also shows four anomalies at the temperatures where the magnetic anomalies appear, confirming the occurrence of successive magnetic transitions. A clear two-step metamagnetic process appears along the easy magnetization direction of the c-axis at low temperatures. The magnetization in the first step is almost constant and is corresponds to (1/5) Ms (Ms: saturation magnetization), indicating that this field-induced phase has a long period and a stable magnetic structure. A metamagnetic process is hypothesized on the basis of the magnetic structure. The B001 − T phase diagram is constructed.

The magnetic measurements in detail, especially high field magnetic measurements up to 45 T, have been performed on a TbPd2Ge2 single crystal. The compound shows an antiferromagnetic ordering below T N =14 K. High field magnetization shows that the magnetic easy direction is the [110] direction in the basal plane. The easy magnetization is saturated above about 25 T at 1.3 K and reaches 9.0 μB/f.u. Multi-step metamagnetic processes appear within the basal plane; that is, three-step and five-step metamagnetic processes appear along the [110] and [100] directions, respectively. The [001] magnetization process is a one-step metamagnetic one. All transitions persist up to near T N . The B 100–T and B 110–T magnetic phase diagrams were constructed, where there are five and three ordered phases, respectively. The crystalline electric field effects were examined. On the basis of the effects, the magnetization behavior has been discussed.

The magnetic characteristics of the single crystal compound TbCu 2 Ge 2 have been studied by magnetic susceptibility and magnetization measurements. The susceptibility shows two anomalies at T N =12.3 K and T t =9.3 K. The magnetic easy direction is the [1 1 0] direction in the basal plane. The magnetization along the easy direction in the basal plane shows a multi-step (at least four steps) metamagnetic process. No significant change of the process is observed at T t . A one-step metamagnetic transition appears around 17 T in the hard c -axis magnetization process. This transition persists above T N up to 25 K where the susceptibility shows a broad peak. The origin is unsolved yet.

We have performed pressure-dependent electrical resistivity measurements of a single crystal Ce 2 Pd 3 Si 5 , which is an antiferromagnetic Kondo lattice compound, at pressures up to 9.5 GPa and at temperatures down to ∼ 0.4 K . As the pressure is increased, the Neel temperature T N deduced from the temperature dependence of resistivity decreases steeply above 4.8 GPa and disappears at P ⩾ 8.6 GPa . Both A and ρ 0 values in Fermi liquid law ρ = ρ 0 + AT 2 at low temperature region increase abruptly above 4.8 GPa and exhibit a plateau at ∼ 9 GPa . These results suggest that non-magnetic state could be formed at P ⩾ 8.6 GPa and that possible quantum critical point might exist at pressures around 9 GPa in this compound. However, there is no sign of superconductivity in resistivity data at the lowest temperature we studied around the possible QCP.

The ferromagnetic compound Fe2P shows a first-order paramagnetic to ferromagnetic transition at TC=209 K. To investigate the magnetic properties of this compound under high pressures above 3 GPa, it has been tried to measure the magnetization using a diamond anvil type high-pressure apparatus by MPMS (quantum design). As the results of trial and error, we have succeeded to obtain the data with sufficient precision to understand the substantial behavior of the compound even under considerable high pressures above 5.0 GPa.

The results of a comprehensive study of the structural, magnetic, and magnetotransport properties of the Heusler compounds ${\text{Ru}}_{2\ensuremath{-}x}{\text{Fe}}_{x}\text{CrSi}$ are presented. The Fe-rich compounds $(x\ensuremath{\ge}1.5)$ exhibit a usual ferromagnetic transition. The Ru-rich compound $(x=0.1)$ does not show ferromagnetism but exhibits a peak in magnetic susceptibility at ${T}_{N}^{\ensuremath{\ast}}=30\text{ }\text{K}$. Nevertheless, specific-heat measurements show that there is no antiferromagnetic transition at ${T}_{N}^{\ensuremath{\ast}}$ nor at any other temperatures. With further decreasing temperature strong irreversible behavior occurs below a temperature ${T}_{g}$. It is proposed that these results can be interpreted as successive spin-glass transitions at ${T}_{N}^{\ensuremath{\ast}}$ and ${T}_{g}$. The compounds with intermediate $x$ ($=0.3$ and 0.5) are found to be ferromagnetic. Both the saturation magnetization and the Curie temperature ${T}_{C}$ increase with increasing $x$. However, being different from the Fe-rich compounds, hysteresis of the magnetization is observed and this suggests that the ferromagnetism has glassy character. In lower-temperature range fairly large negative magnetoresistance are observed. These results are suggestive of a magnetically inhomogeneous ferromagnetic state, that is, the formation of ferromagnetic clusters.

A GW approximation (GWA) method named $\text{U}+\text{GWA}$ is proposed, where we can start GWA with more localized wave functions obtained by the local spin-density approximation $(\text{LSDA})+\text{U}$ method. Then GWA and $\text{U}+\text{GWA}$ are applied to MnO, NiO, and ${\text{V}}_{2}{\text{O}}_{3}$ in antiferromagnetic phase. The band gaps and energy spectra show excellent agreement with the experimentally observed results and are discussed in detail. The calculated width of $d$ bands of ${\text{V}}_{2}{\text{O}}_{3}$ is much narrower than that of the observed one which may be a mixture of ${t}_{2g}^{2}$ multiplet and single-electron ${t}_{2g}$ level. GWA or $\text{U}+\text{GWA}$ does not work also in the paramagnetic phase of ${\text{V}}_{2}{\text{O}}_{3}$ and the reason for this is clarified. The method of the unique choice of on-site Coulomb interaction is discussed in detail. The criterion for whether we should adopt GWA or $\text{U}+\text{GWA}$ is discussed and is assessed with the help of the off-diagonal elements of the self-energy.

The electronic structure of $A$-type antiferromagnetic insulator $\mathrm{La}\mathrm{Mn}{\mathrm{O}}_{3}$ is investigated by the GW approximation. The band gap and spectrum are in a good agreement with experimental observation. The lifetime of electrons in conduction bands is much shorter than that of holes in valence bands. The insulator-to-metal transition with antiferromagnetic-to-ferromagnetic transition with photocarrier injection is attributed to the characteristic properties of excited electron states in $A$-type antiferromagnetic perovskite systems. The onsite $d\text{\ensuremath{-}}d$ Coulomb interaction is strongly screened at the low energy region by mobile ${e}_{g}$ electrons.

Thermal neutron elastic scattering experiments revealed that iron localized moments form in an antiferromagentic short range ordering in LuFe 2 Ge 2 below 9 K. A long range type antiferromagnetic ordering grows rapidly under high pressure above 1.6 GPa.

EuSnP shows an antiferromagnetism below T N = 21 K , in which two metamagnetic transitions were observed with applying magnetic field along both the directions parallel and perpendicular to the c -axis of tetragonal structure. In addition, entropy released up to T N was only ∼ 75 % of R ln 8 which is the value of entropy expected from Eu2+ state. These might bring about novel antiferromagnetic ground state with noncollinear configuration of Eu2+ moments.

SmMIn5 ( M = Co , Rh , Ir ) crystallizes in the tetragonal HoCoGa5-type structure. This type of crystal structure is noticed as tetragonal variants of the AuCu 3 -structure, in which new superconductors were discovered. PuCoGa5 and PuRhGa5 are also the interesting superconductors. On the other hand, it is expected that Sm has a ground state similar to Pu compounds. We have succeeded in growing single crystals of SmMIn5 by the flux method. SmRhIn5 and SmIrIn5 showed the antiferromagnetic ordering and extra transitions below T N , which is almost same as the results in the previous report. We have succeeded in growing single crystals of SmCoIn5. It also showed the antiferromagnetic ordering and extra transitions below T N = 11.9 K . The temperatures of these anomalies are 6, 7.6 and 11.9 K and lowest found in SmMIn5 compounds.

X-ray diffraction measurements on Ce2Fe17 have been performed in the temperature range from 8 to 300 K at the magnetic fields up to 5 T . The thermal expansion curves along the principal axes for antiferromagnet and ferromagnet Ce2Fe17 are presented. A distinct lattice expansion was observed simultaneously with the metamagnetic transition. This suggests that the hybridization between Fe 3d- and Ce 4f-electrons in Ce2Fe17 is suppressed by the application of magnetic field.

High field magnetization measurement were performed up to 45 T using a long pulse magnet on a GdPd2Si2 single crystal compound having the tetragonal ThCr2Si2-type crystal structure and an antiferromagnetic ordering of TN=16.7 K. The magnetization processes are almost typical antiferromagnetic ones with a weak magnetic anisotropy though small anomalies exist in the processes. The magnetization saturates 7 μB/f.u. above Bs=32 T. The B001-T and B100-T magnetic phase diagrams were constructed. There are three phases, the phase I, II and III, under non-magnetic field in the ordered state for both diagrams. The field-induced phase, phase IV, appears below the paramagnetic phase by the [100] magnetic field, B100, which is accompany with a re-entrant behaviour. The B100 makes the phase II be stable and the phase I and III be instable. These strange behaviours indicate the direction of the magnetic moment changes in each phase.

Magnetic characteristics have been studied for a TbPd 2 Si 2 single crystal from measurements of magnetic susceptibility, high field magnetization, and specific heat. The antiferromagnetic ordering below T N =15 K has been confirmed. The easy magnetization direction is the [110] direction in the basal plane at high magnetic fields. The [110] magnetization is saturated above 24 T and reaches M s =9.0 µ B . Multistep metamagnetic behaviors appear in the basal plane magnetization processes. A one-step metamagnetic transition appears in the [001] magnetization process and persists up to 28 K above T N . Strong magnetic anisotropy is observed between the [110] and [100] directions for high fields, and between the [001] and directions in the basal plane. Magnetic phase diagrams are constructed, in which there are four magnetic ordered phases. The main features of anisotropic magnetic behaviors are almost explained by crystalline electric field effects.

Magnetic neutron diffraction measurements were carried out on the heavy-fermion antiferromagnet CeRhIn 5 under hydrostatic pressure. The incommensurate (IC) magnetic ordering is known to be charact...