Journal of Magnetism and Magnetic Materials 2018-04-01

The magnetic state in the binary DyxGe1-x (x ≤ 0.02) alloy semiconductor

K.B. Paul

Index: 10.1016/j.jmmm.2018.03.072

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Abstract

Diluted bulk magnetic alloy semiconductors DyxGe1-x (x ≤ 0.02) were prepared by a two-step fabrication procedure and studied experimentally by XRD, EDX and magnetic methods. The polycrystalline materials had the ccp (cubic closed-packed) structure of the host Germanium up to ≈ 2 at% of Dysprosium. They exhibited different low-temperature and high-temperature behavior. Low-field dc magnetic susceptibility data showed sharp peaks and irreversibility between zero-field cooled and field-cooled states for x < 0.02. A stable antiferromagnetic phase with temperature of the antiferromagnetic to paramagnetic transition TN = 25 K was observed at x = 2 at% of Dysprosium. The solubility range of the binary DyxGe1-x alloy system is limited to ∼ 2 at% due to the large atomic radius of the solute. The low-temperature magnetic phase is characterized as spin-glass below 2 at%. The magnetic relaxation and non-linear susceptibility χnl of Dy0.01Ge0.99 were analyzed, and the spin-glass phase was defined with the critical exponents of the phase transition β = 0.52 ± 0.10, γ = 2.85 ± 0.10 and δ = 6.49 ± 0.02. From the Curie-Weiss behavior of the susceptibility at high temperatures, we determined an average effective Dy-Dy exchange constant J1 = – 6. 90 K and effective magnetic moment per Dy ion µeff = 10.08 µB. The rare-earth Dy atoms behave as isolated in Ge matrix at high-temperatures.