한국자기학회

Y.R. Pan(Department of Materials Science and Engineering, The Pukyong National University), H.W. Kwon(Department of Materials Science and Engineering, The Pukyong National University)

Abstract

The Sm₂Fe₁₇N_x materials were prepared by the combination consisting of the HDDR (hydrogenation, disproportionation, desorption, and recombination) process and nitrogenation or by the conventional way consisting of nitrogenation only, and the magnetic and thermomagnetic properties of the materials were investigated. The magnetic characterisation of the prepared materials was performed using a VSM. Thermal stability of the materials was evaluated using a DTA under Ar gas atmosphere. The thermomagnetic characteristics of the materials were examined using a Sucksmith-type balance. The previously HDDR-treated Sm₂Fe₁₇parent alloy was found to be nitrogenated more easily compared to the ordinary Sm₂Fe₁₇alloy. The Sm₂Fe₁₇N_xmaterial produced by the combination method showed a high coercivity (12.9 kOe) even in the state of coarse particle size (around 60 µm). It was also revealed that the Sm₂Fe₁₇N_xmaterial produced by the by the combination has higher thermal stability with respect to the material produced by convenrional way. The Sm₂Fe₁₇N_xmaterial produced by the combination showed an unusual TMA tracing featured with a low and constant magnetisation at lower temperature range and a peak just before the Curie temperature. This thermomagnetic characteristic was interpreted in terms of the competition between two counteracting effects; the decrease in magnetisation due to the thermal agitation at an elevated temperature and the increase in magnetisation resulting from the rotation of magnetisation of the fine grains comparable to a critical single domain size due to the decreased magnetocrystalline anisotropy at an elevated temperature.

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