Temperature dependence of the magnetostriction and magnetoelastic coupling in Fe100-xAlx (x=14.1,16.6,21.5,26.3) and Fe50Co50

In this paper, we report magnetostriction measurements, (lambda(100)) on Fe-rich Fe-Al alloys and Fe50Co50 as functions of temperature from 77 K to room temperature (RT). From these measurements and elastic constant (c') measurements, the tetragonal magnetoelastic coupling constants (b(1)'s) were calculated. Significant differences were found between our RT measurements and earlier magnetostriction measurements for the higher Al concentration alloys (16.6%, 21.5%, 26.3% Al) and the Fe50Co50 alloy. Reminiscent of the temperature dependence of lambda(100) for pure Fe, magnetostriction changes with temperature are minimal for Fe-Al alloys having the disordered bcc (A2) structure (x < 19% Al). In contrast, the alloy possessing the ordered (D0(3)) structure shows an anomalous decrease in magnetostriction in lambda(100) with decreasing temperature. For the Fe-Al alloy system, the magnetoelastic coupling constant, vertical bar b(1)vertical bar, exhibits a peak at room temperature maximizing at 16.6% Al with a value of 12.3 MJ/m(3). For Fe50Co50, vertical bar b(1)vertical bar was calculated to be similar to 34 MJ/m(3) at room temperature. (C) 2008 American Institute of Physics.