High field specific heat up to 35 T, C-p, and magnetic susceptibility, chi, measurements were performed on the quasi-two-dimensional (2D) Heisenberg antiferromagnet [Cu(pyz)(2)(pyO)(2)](PF6)(2). While no C-p anomaly is observed down to 0.5 K in zero magnetic field, the application of field parallel to the crystallographic ab-plane induces a lambda-like anomaly in C-p, suggesting Ising-type magnetic order. On the other hand when the field is parallel to the c-axis, C-p and chi show evidence of XY-type antiferromagnetism. This dependence upon the field orientation occurs because the extreme two-dimensionality allows the intrinsic (zero field) spin anisotropy to dominate the interlayer coupling, which has hitherto masked such effects in other materials.
Original Publication Title
Physical Review B
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Kohama, Yoshimitsu; Jaime, Marcelo; Ayala-Valenzuela, Oscar E.; McDonald, Ross D.; Mun, Eun deok; Corbey, Jordan F.; and Manson, Jamie L., "Field-Induced Xy And Ising Ground States In A Quasi-Two-Dimensional S=1/2 Heisenberg Antiferromagnet" (2011). Chemistry and Biochemistry Faculty Publications. Paper 16.