Abstract
All ferromagnetic materials show deterioration of magnetism-related properties such as magnetization and magnetostriction with increasing temperature, as the result of gradual loss of magnetic order with approaching Curie temperature TC. However, technologically, it is highly desired to find a magnetic material that can resist such magnetism deterioration and maintain stable magnetism up to its TC, but this seems against the conventional wisdom about ferromagnetism. Here we show that a Fe–Ga alloy exhibits highly thermal-stable magnetization up to the vicinity of its TC, 880 K. Also, the magnetostriction shows nearly no deterioration over a very wide temperature range. Such unusual behaviour stems from dual-magnetic-phase nature of this alloy, in which a gradual structural-magnetic transformation occurs between two magnetic phases so that the magnetism deterioration is compensated by the growth of the ferromagnetic phase with larger magnetization. Our finding may help to develop highly thermal-stable ferromagnetic and magnetostrictive materials.
Highlights
All ferromagnetic materials show deterioration of magnetism-related properties such as magnetization and magnetostriction with increasing temperature, as the result of gradual loss of magnetic order with approaching Curie temperature TC
Temperature-independent magnetization has never been achieved in any single-phase ferromagnetic material since it is against the basic law of magnetism
The solution-treated sample is in metastable state, where A2, B2 and DO3 phases coexist, as shown by the selected area electron diffraction (SAED) pattern
Summary
All ferromagnetic materials show deterioration of magnetism-related properties such as magnetization and magnetostriction with increasing temperature, as the result of gradual loss of magnetic order with approaching Curie temperature TC. For a given magnetic material, the usual intrinsic approach to achieve thermally stable magnetization is to enhance TC through alloying It may, deteriorate other related magnetic properties, for example, the magnetostriction that is a fundamental property of ferromagnets referring to the macrostrain induced by an external magnetic field. We shall show that an aged Fe73Ga27 alloy, containing both L12 phase and remanent bcc phases, exhibits highly thermal-stable magnetization up to its TC (B880 K) and stable magnetostriction over a wide temperature range. Such unusual behaviours stem from simultaneous magnetic/structural transformations from bcc into L12, which offsets the thermally induced magnetization reduction. The highly thermal-stable magnetization and magnetostriction may lead to numerous hightemperature applications
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