Stress induced magnetic anisotropy and coercivity in Fe73.5Cu1Ta3Si13.5B9 amorphous alloy

The magnetic anisotropy induced by stress annealing (500 MPa) in Fe73.5Cu1T a3Si13.5B9 amorphous alloy has been investigated. Such thermal treatment wa s carried out by means of the Joule heating technique (current density rang ing from 20 to 40 A/mm(2)). As a result, a uniaxial in-plane magnetic aniso tropy was induced in the samples. The dependence of this induced anisotropy on the current density shows a maximum (1000 J/m(3)) around 34 A/mm(2), wh ich can be connected to the first stages of the crystallization process, fo llowed by a minimum at 37 A/mm(2). The coercive field increases with this k ind of thermal treatment, and is around 10-15 A/m for the optimum nanocryst alline state, which is one order of magnitude larger than that reported for this nanocrystalline material treated in conventional furnace. The variati ons of the coercive field after stress annealing seem to be correlated to t he induced magnetic anisotropy behavior. The minimum anisotropy occurs for the optimum nanocrystallization process. The induced anisotropy should be m ainly understood as of magneto-elastic character arising in the FeSi grains due to internal stresses. (C) 2000 American Institute of Physics. [S0021-8 979(00)02724-9].