HYSTERETIC BEHAVIORS OF FIRST-ORDER PHASE TRANSITION MAGNETOCALORIC MATERIALS

摘要

The hysteretic behavior of some first-order magnetic phase transition materials with large magnetocaloric effect has been investigated by means of magnetic measurements. An unusual phase transition, so called 'virgin' effect, exists in some Mn-based compounds, but not in the Gd_5(Si,Ge)_4 and La(Fe,Si)_(13) compounds. In thermal hysteretic regime, the magnetic behavior of the first-order phase transition materials strongly depends on the history of thermal and field cycles. A reversible field-induced phase transition is important for producing a reversible large magnetocaloric effect. The mechanism of thermal hysteresis is discussed on the basis of Landau theory by taking into account the coupling between magnetization and strain.