Induced magnetic anisotropy in Co-Mn-Si-B amorphous microwires

The effect of both thermal treatments as well as chemical etching treatment s on the magnetic behavior has been investigated in nearly-zero magnetostri ction glass-coated amorphous (Co1-xMnx)(75)Si10B15 (x = 0.08, 0.09, and 0.1 0) microwires. Such a small change in x results in rather strong changes in the hysteresis loop parameters including coercitivity, H-c, and initial ma gnetic permeability, mu(15). This effect was ascribed to the change of sign of the magnetostriction constant with a proper combination of the coercivi ty and relatively high initial permeability for the as-cast x = 0.09 sample . Thermal treatment (temperatures 100-200 degrees C for 0.5-2 h) as well as chemical etching in 20% diluted fluoridric acid with duration from 0.5 up to 50 min modify this magnetic parameters owing to the internal stresses re laxation process. In particular, annealing under applied magnetic field (fi eld annealing) can improve more significantly these magnetic parameters: in creasing both H-c and mu(15). Such phenomenology can be interpreted conside ring the noticeable longitudinal magnetic anisotropy induced by the combine d effects of the magnetic field and strong internal stresses arising from t he coating during the thermal treatment. The reduction of the glass coating thickness by chemical etching leads to a decrease of the internal stresses from a coating and, consequently, to a decrease of the transverse magnetoe lastic anisotropy. Such decrease of anisotropy plays a role similar to that induced by field annealing on the hysteretic behavior. (C) 2000 American I nstitute of Physics. [S0021-8979(00)09403-2].