Exchange Bias in Dilute Magnetic Alloys

The dilute magnetic alloys Cu_1-xMn_x and Ag_1-xMn_x (0 < x < 0.3) show exchange-biased hysteresis loops after field-cooling to low temperature. These shifted hysteresis loops are accompanied by abrupt magnetization jumps, ΔM, at field strengths, defining the exchange-bias field and coercivity. The exchange-biased hysteresis loops can be phenomenologically described by a unidirectional and a uniaxial anisotropy contribution. At low temperatures and moderate field strengths, only the unidirectional component exists, whereas at higher fields, a uniaxial component introduces coercivity and losses to the loops. The observed anisotropy is accounted for by the Dzyaloshinsky–Moriya interaction and the chirality of the interacting spin pairs. Here, a concise review of the phenomenology and models developed for the observations of exchange anisotropy in dilute magnetic alloys in the second half of the last century is given. Recent findings on the cooling field dependence of the exchange bias of Mn-based dilute magnetic alloys provide new insights on the phenomenon.