Development and magnetic properties of an alloy that can change from very soft to semi-hard magnetic are reported. We found that as quenched ribbons of Fe75.3Pt8B12P4Cu0.7 alloy are amorphous by X-ray. Heat treatment in the temperature range of 400-450°C causes formation of many α-Fe grains in the amorphous matrix. Hard magnetic L10 FePt grains appear at ∼520°C. This alloy shows a high saturation magnetic flux density [Bs (≈ Ms)>1.55T] along with the ability to vary coercivity (Hc) from ∼25A/m to 11000A/m. The Hc can be increased further to more than 21000A/m, but at the expense of a significant decrease in Bs. The ability to control magnetic properties lies in a precise control over the soft and hard magnetic phases, which are strongly exchange coupled.
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