Structure and magnetic properties of (Fe0.5Co0.5)(88)Zr7B4Cu1 nanocrystalline alloys

The development of Fe73.5Si13.5B9Nb3Cu1 (FINEMET) by Yoshizawa et al. and F e88Zr7B4Cu1 (NANOPERM) by Inoue et al. have shown that nanocrystalline micr ostructures can plan an important role in the production of materals with o utstanding soft magnetic properties. The FINEMET and NANOPERM materials rel y on nanocrystalline alpha-Fe3Si and alpha-Fe, respectively, for their soft magnetic properties. The magnetic properties of a new class of nanocrystal line magnets are described herein. These alloys with a composition of (Fe, Co)-M-B-Cu (where M = Zr and Hf) are based on the alpha- and alpha'-FeCo ph ases, have been named HITPERM magnets, and offer large magnetic inductions to elevated temperatures. This report focuses on thermomagnetic properties, alternating current (ac) magnetic response, and unambiguous evidence of al pha'-FeCo as the nanocrystalline ferromagnetic phase, as supported by synch rotron x-ray diffraction. Synchrotron data have distinguished between the H ITPERM alloy, with nanocrystallites having a B2 structure data have disting uished between the HITPERM alloy, with nanocrystallites having a B2 structu re from the FINEMET alloys, with the D0(3) structure, and NANOPERM alloys, with the A2 structure. Thermomagnetic data shows high magnetization to pers ist to the alpha --> gamma phase transformation at 980 degrees C. The room temperature ac permeability has been found to maintain a high value of 1800 up to a frequency of similar to 2 kHz. The room temperature core loss has also been shown to be competitive with that of commercial high temperature alloys with a value of 1 W/g at B-s = 10 kG and f = 1 kHz. (C) 1998 America n Institute of Physics. [S0021-8979(98)03024-2].