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[摘要]：Single crystals of MAl(2)S(4) (M = Mn(2+), Fe(2+), Co(2+)) were synthesized using the chemical vapor transport method and characterized using high-resolution synchrotron X-ray diffraction to determine the structure. All the compounds have a layered slab structure separated by a van der Waals gap, which results in highly two-dimensional magnetism. Magnetic susceptibility measurements indicate spin-glass behavior below T(o)* values of similar to 2 K, similar to 10.5 K, and similar to 5 K for MAl(2)S(4) (M = Mn(2+), Fe(2+), Co(2+)), respectively, and heat capacity measurements indicate no long-range magnetic ordering observed down to 0.4 K. These results can be attributed primarily to site disorder due to mixing of M(2+) and Al(3+) ions (M = Mn(2+), Fe(2+), Co(2+)) and low dimensionality with geometrical frustration also playing a role. Interestingly, MnAl(2)S(4), with almost isotropic S = 5/2 spin, has the highest frustration parameter among the series of compounds and is a possible candidate for a two-dimensional Heisenberg spin glass system. |
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