Abstract
Magnetic and thermal hysteresis (difference in magnetic properties on cooling and heating) have been studied in polycrystalline Dy (dysprosium) between 80 and 250 K using measurements of the reversible Villari effect and alternating current (AC) susceptibility. We argue that measurement of the reversible Villari effect in the antiferromagnetic phase is a more sensitive method to detect magnetic hysteresis than the registration of conventional B(H) loops. We found that the Villari point, recently reported in the antiferromagnetic phase of Dy at 166 K, controls the essential features of magnetic hysteresis and AC susceptibility on heating from the ferromagnetic state: (i) thermal hysteresis in AC susceptibility and in the reversible Villari effect disappears abruptly at the temperature of the Villari point; (ii) the imaginary part of AC susceptibility is strongly frequency dependent, but only up to the temperature of the Villari point; (iii) the imaginary part of the susceptibility drops sharply also at the Villari point. We attribute these effects observed at the Villari point to the disappearance of the residual ferromagnetic phase. The strong influence of the Villari point on several magnetic properties allows this temperature to be ranked almost as important as the Curie and Néel temperatures in Dy and likely also for other rare earth elements and their alloys.
Highlights
Dy and other rare earth elements have unique physical and chemical characteristics which make them indispensable in numerous existing and innovative applications
Based on the experimental results obtained, we suggest that the thermal hysteresis in
We showed that mechanomagnetic spectroscopy is much more sensitive to magnetic hysteresis in the AFM phase than the conventional experimental method based on registration of
Summary
Dy (dysprosium) and other rare earth elements have unique physical and chemical characteristics which make them indispensable in numerous existing and innovative applications. Dy exhibits a transition at the Néel temperature, TN = 178 K, between the paramagnetic (PM) and helical-type antiferromagnetic (AFM) structure and an antiferro-ferromagnetic (FM) transition near 85 K on cooling (Curie temperature, TC ) [1,2,3]. The latter is a first order magnetostructural transition, since the high-temperature hexagonal lattice undergoes orthorhombic distortions [4,5]. A related problem pending interpretation is the difference in behavior of Dy and other rare earths and their alloys in the AFM state for cooling and heating from the FM phase [20,21,22,23]
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