Design and preparation of a bulk magnet exhibiting an inverted hysteresis loop

We report on a magnet exhibiting an inverted magnetic hysteresis loop, i.e., the magnetization becomes negative in the decreasing part even when the applied field is still positive, while the magnetization becomes positive in the increasing part when the applied field is still negative. The key to obtaining this unusual magnet is to utilize a competing effect between the spin-flip transition and the uniaxial magnetic anisotropy. On the basis of the model calculations considering this effect, we have succeeded in synthesizing a bulk magnet showing the inverted magnetic hysteresis loop with the system of samarium(III) gadolinium(III) hexacyanochromate(III).