Strain-Induced Exchange Bias Effects in Chemically Ordered ${\hbox {Pt}}_{3}{\hbox {Fe}}$ Single Crystal

Magnetic hysteresis loops have been studied in chemically ordered Pt₃Fe single crystals after plastic deformation with various levels of strain up to 29.8%. Plastic deformation results in changes of atomic arrangement around glide plane of superlattice dislocations and induces ferromagnetism even at room temperature. We find that magnetic hysteresis loops after field cooling are shifted toward a negative field unlike normal hysteresis loops centered at the origin after zero-field cooling. This shift rapidly decreases with increasing temperature and disappears above T _N1= 170 K, which is paramagnetic-antiferromagnetic transition temperature of L1₂ superlattice structure. The results clearly demonstrate the exchange bias effects below T _N1 in deformed Pt₃Fe single crystals, where ferromagnetic domains produced around glide plane are magnetically coupled with antiferromagnetic L1₂ matrix.