[en] The authors have measured magnetic susceptibility, thermal expansion, electrical resistivity, and magnetoresistance of the intermetallic compound YMn₂. YMn₂ orders antiferromagnetically below T_N ≅ 110 K. There is a large thermal hysteresis such that the ordering temperature is T_N = 86 K on cooling and T_N = 116 K on warming. This is a first-order phase transition from the paramagnetic to antiferromagnetic phase. Their electrical resistivity and magnetoresistance measurements in the ordered state show a localized magnetic moment for Mn atoms in YMn₂ below T_N. The Mn moments collapse at T_N which is reflected in the sharp decrease in the thermal expansivity at T_N. Above T_N the Mn moment gradually recovers with increasing temperature which is reflected as an increase in χ with increasing temperature in the paramagnetic state. This behavior at T > T_N could be described by weak itinerant electron magnetism

[en] In this paper, high gradient magnetic separation of copper-oxide superconducting particles in a gas-fluidized bed is studied experimentally. Particles over the size range 45-105 μm exhibit classical behavior when fluidized with He gas at 77 K, whereas the more cohesive, smaller particles were difficult to fluidize. Separation experiments on a uniform mixture of tetragonal and orthorhombic phases have shown that 30 min of exposure to the field gradient is sufficient to equilibrate the superconductor concentration profile. In addition, the equilibrium separation data reveal that best separation is achieved at three times the minimum fluidization gas velocity U_mf. This is consistent with the behavior of fine powders where the interparticle frictional forces are minimized at 3 U_mf. Observed results are discussed in terms of a collective effect of Meissner and interparticle friction

[en] Series representations for the average magnetization anti M are obtained from the known analytic solutions of the Bean model. It is found that at relatively high fields, anti M has the same functional dependence on H as J_c. A power law behavior of anti M is found experimentally for YBCO powder samples, which indicates J_c has a similar power law dependence. (orig.)