Abstract
The anisotropic antiferromagnet FeF2 has been extensively used as an antiferromagnetic layer to induce exchange bias effects in ferromagnetic/antiferromagnetic bilayers and heterostructures. In this work, an apparent exchange bias occurring in the low temperature hysteresis loops of FeF2 single crystals is investigated. A detailed investigation of the hysteresis and remnant magnetization indicates that the observation of an apparent exchange bias in FeF2 stems from an intrinsic excess moment associated with a distortion of the antiferromagnetic structure of piezomagnetic origin.
Highlights
The anisotropic antiferromagnet FeF2 has been extensively used as an antiferromagnetic layer to induce exchange bias effects in ferromagnetic/antiferromagnetic bilayers and heterostructures
In Fe0.46Zn0.54F2, the hysteresis (M-H) curves were found to include an excess moment under field cooled (FC) conditions, somewhat similar to that observed in dilute magnetic alloys such as Ni(Mn), Cu(Mn), Ag(Mn), where a unidirectional anisotropy leads to horizontally shifted hysteresis loops, reminiscent of exchange bias effects[11,12,13,14,15]
We show that an apparent exchange bias observed in the low temperature hysteresis loops of single crystals of FeF2 originates from a vertical shift of the loops due to an intrinsic excess moment associated with a distortion of the antiferromagnetic structure appearing when passing through TN in a finite magnetic field
Summary
The anisotropic antiferromagnet FeF2 has been extensively used as an antiferromagnetic layer to induce exchange bias effects in ferromagnetic/antiferromagnetic bilayers and heterostructures. A detailed investigation of the hysteresis and remnant magnetization indicates that the observation of an apparent exchange bias in FeF2 stems from an intrinsic excess moment associated with a distortion of the antiferromagnetic structure of piezomagnetic origin. The strongly anisotropic uniaxial antiferromagnet FeF2 is an almost ideal realization of a 3d-Ising model system. It exhibits an antiferro- to paramagnetic transition across the Néel temperature TN = 78.4 K2. We show that an apparent exchange bias observed in the low temperature hysteresis loops of single crystals of FeF2 originates from a vertical shift of the loops due to an intrinsic excess moment associated with a distortion of the antiferromagnetic structure appearing when passing through TN in a finite magnetic field
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