Hysteresis of magnetostructural transitions: Repeatable and non-repeatable processes

• Published in: Physica. B, Condensed matter Condensed matter, 2014-02, Vol.435, p.138-143
• Main Authors: Provenzano, Virgil, Della Torre, Edward, Bennett, Lawrence H., ElBidweihy, Hatem
• Format: Article
• Language: English
• Subjects: Condensed matter; Cycles; Heusler alloys; Hysteresis; Magnetic properties; Magnetostructural transitions; Mathematical models; Refrigerants; Refrigeration
• ISSN: 0921-4526; 1873-2135
• DOI: 10.1016/j.physb.2013.09.056

The Gd5Ge2Si2 alloy and the off-stoichiometric Ni50Mn35In15 Heusler alloy belong to a special class of metallic materials that exhibit first-order magnetostructural transitions near room temperature. The magnetic properties of this class of materials have been extensively studied due to their interesting magnetic behavior and their potential for a number of technological applications such as refrigerants for near-room-temperature magnetic refrigeration. The thermally driven first-order transitions in these materials can be field-induced in the reverse order by applying a strong enough field. The field-induced transitions are typically accompanied by the presence of large magnetic hysteresis, the characteristics of which are a complicated function of temperature, field, and magneto-thermal history. In this study we show that the virgin curve, the major loop, and sequentially measured MH loops are the results of both repeatable and non-repeatable processes, in which the starting magnetostructural state, prior to the cycling of field, plays a major role. Using the Gd5Ge2Si2 and Ni50Mn35In15 alloys, as model materials, we show that a starting single phase state results in fully repeatable processes and large magnetic hysteresis, whereas a mixed phase starting state results in non-repeatable processes and smaller hysteresis.