Bistable and multidomain state of $\alpha$-Fe/(PrDy)(FeCo)B ferromagnetic microwires

Microwire of $\alpha$-Fe(50 at.%)(PrDy)(FeCo)B(48 at.%) was obtained by extracting a hanging melt drop of (PrDy)(FeCo)B in an electron beam. It was shown that a single microwire with a diameter of 50 $\mu$m and a length of 0.8 – 6 mm with an amorphous phase (PrDy)(FeCo)B content of $\sim$48% and a polycrystalline $\alpha$-Fe phase of $\sim$52% has a rectangular narrow magnetic hysteresis loop and, accordingly, a bistable state with a switching field of $\sim$100 Oe. The shortening of the wire to $\sim$0.6 mm leads to a sharp deviation from the squareness of the loop, reducing the slope of the dependence of the magnetization on the field and the coercive force to 20 Oe. In the subsurface layers consisting of the amorphous phase (PrDy)(FeCo)B, oriented areas of reverse magnetization are observed. The role of the magnetic dipole interaction in the formation of a magnetic hysteresis loop of chaotic microwire assemblies of various compositions is discussed.