Yuzo Hashimoto

Magnetic Properties of Rare Earth Copper Intermetallic Compounds, RCu2. II. Light Rare Earth

Measurements of magnetization and susceptibility have been made on single crystals of heavy rare earth copper compounds, RCu 2 . All these compounds show metamagnetism with a relative low critical field at 4.2 K. The paramagnetic Curie temperatures along each principal axis are anisotropic. The crystal field parameters V 2 0 and V 2 2 are determined from the values of anisotropic paramagnetic Curie temperatures on the basis of the molecular field theory. These values are in agreement with those evaluated from a point charge model. The neutron diffraction measurements on a TbCu 2 single crystal confirm the collinear magnetic structure.

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.

Magnetic Anisotropy in the Binary Alloys of Gd with the Other Heavy Rare Earth Metals

The magnetizations of the single crystalline binary alloys of Gd with the other heavy rare earth metals, R(=Dy, Ho and Er), were measured at 4.2 K in applied fields up to 54 kOe along the three principal crystallographic directions. The magnetocrystalline anisotropy constants K 0 2 and K 0 4 were determined from the analysis of the hard magnetization curves on the basis of the molecular field theory. The anisotropy constants K 0 2 and K 0 4 were found to vary quadratically with R concentrations. From these results, it is concluded that the magnetic anisotropy of rare earth metals is attributed to the anisotropic exchange interaction as well as the single ion anisotropy.

Ferromagnetic Spin-Coupling of Several Homo- and Mixed-Metal Complexes

Abstract Our studies on polynuclear metal complexes with ferromagnetic spin-coupling are described; (1) Tetranuclear Cu(II) and Ni(II) complexes with cubane structure, (2) mixed-metal complexes with imidazolate bridge, and (3) mixed-metal complexes with oxalate or dithiooxalate bridge.

Magnetic characteristics of PrCd single crystal

Abstract Magnetic measurements have been made along the [100], [110] and [111]-axes of PrCd single crystal in magnetic fields up to 70 kOe in the temperature range from 4.2 to 300 K. PrCd shows metamagnetism below T t = 25 K in which two critical fields are observed in the magnetization processes along the [110] and [111]-axes and a critical field along the [100]-axis. The metamagnetic behaviour is interpreted by a noncollinear antiferromagnetic model with the Pr moments of ∼ 2μ B directed to the 〈111〉-axes.

Magnetic phase transition of DyCu2 induced by high magnetic fields

A magnetic phase transition is induced in the DyCu 2 compound when high magnetic fields are applied along the c-axis. After the transition was induced, the observed magnetization curve along the c-axis direction becomes the same as that obtained along the a-axis. The translated state is retrieved in the initial one by annealing the sample.

Sublattice magnetization and magnetization process in TbCu2

Abstract The TbCu 2 compound exhibits antiferromagnetism and has two nonequivalent Tb sites below 54 K (= T N ). The magnetization for the a -axis increases discontinuously at critical field and saturates at high fields. The magnetization process and magnetic moments have been analyzed in terms of the molecular field theory including the crystal-field interaction.

[{Mn(salen)CN}n]: die erste metamagnetische, eindimensionale Kette mit alternierenden High-spin- und Low-spin-MnIII-Zentren

Ferromagnetische und antiferromagnetische Wechselwirkungen innerhalb bzw. zwischen den Ketten fuhren zu Metamagnetismus in [{Mn(salen)CN}n] (salen=Bis(salicyliden)ethylendiamid), dem ersten eindimensionalen Koordinationspolymer, in dem alternierend High-spin- (S=2) sowie Low-spin-MnIII-Zentren (S=1) vorliegen, verbruckt uber Cyanogruppen (siehe schematische Darstellung).

Magnetic Phase Transition in DyNi2Si2

Magnetic ordering and magnetic phase transition in DyNi2Si2 have been studied by neutron diffraction measurements on powder and single crystal specimens. This compound has an order-to-order phase transition at about 3.5 K, below under the Neel temperature. Experimental results indicated that the phase transition is a first-order transition from a commensurate square-wave type modulation in the c-plane with the two-dimensional propagation vectors k=(1/2±τ, 1/2\mpτ, 0) with τ=0.125=1/8 just below TN to a sine-wave type structure with τ=0.132 which is incommensurate with the lattice periodicity.

Magnetization process of metamagnetic TbCu2 single crystal

Abstract Measurements of the magnetization have been made on the single crystal TbCu 2 compound in the temperature range from 4.2 to 55 K. The magnetization process shows metamagnetic behaviour only for the a -axis, and the magentization for the b and c -axis increase almost linearly with small gradients up to 50 kOe at all temperatures. The compound exhibits strong magnetocrystalline anisotropy. The magnetization processes have been analyzed in terms of the molecular field theory including the crystal-field interaction.