We investigated the substitution effects of Al3+ for Cr3+ on the structure and magnetic, properties of delafossite oxide CuCrO2, which possesses a quasi-2D Heisenberg triangular antiferromagnetic (AFM) lattice. The lattice parameters was found to vary according to the Vegard’s rule. We also found that the large local lattice distortion, caused by the nonmagnetic dopant with different radii between magnetic and nonmagnetic ions, affects the samples significantly. Magnetization and specific heat measurements indicated that AFM ordering is diluted by the substitution of nonmagnetic Al3+ for Cr3+ (S = 3/2). [...]
The tetragonal compound UNi2Si2 exhibits in zero magnetic field three different antiferromagnetic phases belowT N=124 K. They are formed by ferromagnetic basal planes, which are antiferromagnetically coupled along thec-axis with the propagation vectorq=(0, 0, q z). Two additional order-order magnetic phase transitions are observed below T N, namely atT 1=108 K and T 2=40 K in zero magnetic field. All three phases exhibit strong uniaxial anisotropy confining the U moments to a direction parallel to the c-axis. UNi2Si2 single crystals were studied in detail by measuring bulk thermodynamic properties, such as thermal expansion, resistivity, susceptibility, and specific heat. A microscopic study using neutron diffraction was performed in magnetic fields up to 14.5 T parallel to the c-axis, and a complex magnetic phase diagram has been determined. Here, we present the analysis of specific-heat data measured in magnetic fields up to 14 T compared with the results of the neutron-diffraction study and with other thermodynamic properties of UNi2Si2.
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