B. Cage et al., Three-dimensional antiferromagnetism in triamminodiperoxychromate, Cr(NH3)(3)(O-2)(2): a precursor to a new class of Cr(IV) magnets, SOL ST COMM, 119(10-11), 2001, pp. 597-601
This study presents the first observation of long-range antiferromagnetic o
rder in a simple Cr(IV)-peroxo, S = 1 complex. Magnetic susceptibility, chi
, and heat capacity, C-p, results are presented for both powders and single
crystals of triamminodiperoxychromate, Cr(NH3)(3)(O-2)(2). For the investi
gated compound, the spin state of S = 1 was determined by analysis of chi f
rom 2 to 200 K, and correlated with the entropy expected for such a system
as determined by C-p measurements from 2.5 to 20 K. Sharp lambda -like tran
sitions were observed in both chi and C-p, with maxima at 8.80 and 8.46 K,
respectively; characteristic of three-dimensional long-range antiferromagne
tic ordering. The chi and C-p results correlated well using the Fisher heat
capacity relationship. Further analysis of C-p determined that the majorit
y of the spin entropy is engaged at temperatures below 8.46 K. This class o
f compounds might serve as precursors for CrO2 related materials. (C) 2001
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