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Magnetic phase diagram of GdAg1−xZnx

1981; Elsevier BV; Volume: 25; Issue: 2 Linguagem: Inglês

10.1016/0304-8853(81)90110-4

1873-4766

U. Köbler, Wolfgang Kinzel, W. Zinn,

nanoparticles nucleation surface interactions

The magnetic phase diagram of GdAg1−xZnx, an intermetallic solid solution of an antiferromagnet (GdAg: TN = 136 K) and a ferromagnet (GdZn: TC = 269 K), has been elaborated from magnetization measurements. The antiferromagnetic phase boundary TN(x) first passes a broad maximum meeting the ferromagnetic phase boundary TC(x) at x1 = 0.575 and T1 = 72 K, where four phases coexist. On approaching (x1, T1) along TN(x) the magnetization phenomena vanish. At x1 the phase transition still has ferromagnetic appearance but proceeds into a state without spontaneous magnetic moment. Two different ferromagnetic phases (F1, F2) and one ferrimagnetic phase (F3) occur in the composition intervals 0.69 < x1 <1, and 0.61 <x2 < 0.69 and 0.51 < x3 < 0.61. All phase transitions seem to be of second order except th e F1−F2 one at x = 0.69 which is of first order. This phase line meets the paramagnetic to ferromagnetic phase boundary TC(x) in a multicritical point with the coordinates xm = 0.69, Tm = 123 K. Six further mixed magnetic phases, M1, 2, ..., 6, are observed between x = 0.33 and 0.6 below the antiferromagnetic branch and exhibit irreversible thermodynamic properties, such as hysteresis, below about 40 K. Assuming local magnetic interactions only between nearest and next-nearest Gd neighbours, the TN(x) and TC(x) phase boundaries can be described fairly well by a simple model calculation using different exchange parameters for a few relevant distributions of Ag and Zn atoms.