Exchange bias and its phase reversal in the zero magnetization admixed rare earth intermetallics

摘要

Exchange bias effect is an important attribute in several deviceapplications. Traditionally, it is discussed as a form of exchange anisotropyat the interface between the ferromagnetic/antiferromagnetic layers of twodistinct systems. We report here on the magnetically ordered alloys possessingthe feature of unidirectional anisotropy, which reverses its sign across acharacteristic temperature. These are admixed rare earth intermetallics,comprising two dissimilar rare earth (RE) ions, belonging to the two differenthalves of the 4f-series and imbibing the notion of ferromagnetic couplingbetween the spins of all 4f-rare earth ions and that of the conductionelectrons. Magnetic moments of dissimilar RE ions in such admixed alloys,however, get antiferromagnetically coupled and they display magneticcompensation feature such that the field induced reversal in the orientation ofthe magnetic moments of dissimilar rare earth ions happens across thecompensation temperature (Tcomp). Above a threshold field, the conductionelectron polarization also reverses its sign across Tcomp, this is argued tocorrelate with the observed phase reversal in the exchange bias field.