Magnetic frustration in the mixed garnets (FexCr1-x)2Ca3(GeO4)3: the phase diagram and relaxation of the antiferromagnetic long-range order

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Abstract
The authors present the results of powder neutron diffraction studies of the partially frustrated compounds (FexCr1-x)2Ca3(GeO4)3 for x in (0,1). A phase diagram is deduced from measurements of the sublattice magnetisation as a function of temperature. Three phases can be distinguished at T=2 K: for samples in the composition ranges 0p4122 for x=1, I4'1/ac'd for x=0). From a careful peak width analysis the authors obtain clear support for the results of their magnetisation measurements, that for compositions x in the interval )0.4, 0.6( and Tg<or approximately=4 K a reentrant spin glass phase exists. They find for samples in this intermediate-concentration range, that both the long-range-order Bragg components and the magnetic diffuse scattering contribution are dependent on time, on a minute-to-hour timescale. This relaxation phenomenon depends strongly on the cooling history.