High-pressure magnetic study of Fe-Ni and Fe-Pt Invar alloys

Abstract

International audienceMagnetic properties of Fe64Ni36 and Fe-Pt Invar alloys under high pressure have been investigated through x-ray magnetic circular dichroism XMCD up to 12 GPa at ambient temperature and superconducting quantum interference device magnetometer up to 1 GPa for different isotherms, from 10 to 300 K. Results obtained with both techniques on Fe-Pt samples can be well interpreted through the 2-state interpretation of the Invar effect. For the Fe64Ni36 alloy, the relative evolution of the iron magnetic moment at 300 K, measured through XMCD, shows the existence of a plateau between 4 and 10 GPa, also expected within this approach. In the low-pressure range, the evolution of magnetization indicates that the itinerant character of Fe-Ni alloys may affect the transition

Direct measurement of magnetization isotherms of Fe64Ni36Invar alloy in a diamond anvil cell

“…[16] The pressure dependence of Fe-moment determined by analysis of the XES spectra demonstrates the existence of two magnetic transitions in the Fe 64 Ni 36 Invar alloy that take place in pressure ranges from 2 to 5 GPa and from 12 to 15 GPa, respectively, supporting the HS-LS theoretical model. [16] The results of the X-ray Magnetic Circular Dichroism (XMCD) studies of the Fe 72 Pt 28 alloy up to 12 GPa [17] supported conclusions of the HS-LS concept. However, in the case of the Fe 64 Ni 36 Invar alloy, the observed decrease in the normalized integral of XMCD at a pressure range from 3 to 5 GPa was not so unambiguous.…”

Volume and structural study of Fe64Mn36 anti-ferromagnetic Invar alloy under high pressure

“…However, the pressure dependence of the bulk modulus of antiferromagnetic Fe-based Invar alloys such as Fe-Mn and Fe 50 Ni 37 Mn 13 has not yet been clarified [1,14]. The pressure dependence of the bulk modulus of anti-ferromagnetic Mn-based small CTE compounds has also not been clarified [15,16].…”

“…This is because some theoretical and experimental studies have suggested that the relationship between the pressure dependence of the bulk modulus and its magnetic states is closely related to the origin of the anomalous CTE behavior [6][7][8][9][10][11][12][13].…”

Effects of fluence and fluence rate of proton irradiation upon magnetism in Fe65Ni35 Invar alloy

“…Many fundamental studies have been conducted on such materials since the discovery of low thermal expansion in Fe 64 Ni 36 in 1897 [8,9]. Fe-Ni Invar alloys are anomalous not only in terms of low thermal expansion but also in terms of pressure-induced magnetic phase transition [10][11][12][13], and a poorly understood "hidden" excitation that differs from the Stoner excitation [14]. According to the theoretical calculation for Fe-Ni Invar alloy, the energy difference between a high-spin state (HS) with a large volume and a low-spin state (LS) with a small volume is relatively small [15].…”