Elasticity and antiferromagnetism of metallic antiferromagnetics

Abstract

If an antiferromagnetic is spontaneously deformed on cooling through the Néel temperature, then the application of an external stress results in a redistribution of domain vectors, e.g. they may rotate or antiferromagnetic domain walls may move. This causes an additional strain component which will be apparent as an anomalous variation of the Young's modulus with the temperature. The results of measurements of the temperature dependence of Young's modulus for antiferromagnetic γ-CuMn alloys and mixed phase (α + γ) CuMn alloys are reported. The (α + y) alloys show (a) a Young's modulus variation of the expected form which is due to the contained α-Mn, (b) a Young's modulus anomaly at about 130 °K associated with the precipitated γ-CuMn (containing 40 atomic percent Mn). It is shown that the latter phase below 130 °K exhibits ferromagnetic characteristics. A smooth temperature variation of Young's modulus has been obtained for Pd which is consistent with the assumption that Pd is not antiferromagnetic at low temperatures