A study of the magnetic resonance in a single-crystalNi50.47Mn28.17Ga21.36 alloy

Abstract

The single-crystal non-stoichiometric magnetic shape memory alloyNi1−x−yMnxGay with x = 0.2817, y = 0.2136 is studied using magnetic resonance spectroscopy: ferromagnetic resonance (FMR) andconduction electron spin resonance (CESR). The temperature dependence of the integralintensity, the resonance field and the line-width are measured across the wide temperatureinterval from 4.2 to 570 K. Three phase transformations are found in this alloy: with a Curie temperature of 360 K, austenite-to-martensite (direct withTms = 312 K and reversewith Tas = 313 K), and atransformation at T = 45 K, suggestive of the spin-glass state. The angular dependence of the FMR signals is measuredin the martensitic and austenitic states before and after the martensite-to-austenitetransition. The experimental data are used for determination of the magnetizationMm and anisotropyparameters K1 and K2 in the martensitic state. The obtained coefficientK2 is determined to be not small and, moreover, it is comparable withK1. Thetemperature dependence of the resonance signals is also investigated at temperatures significantly higherthan TC, where FMR was transformed to CESR. In the paramagnetic austenitic state (aboveTC) the alloy reveals an extremely intensive signal of CESR, which suggests a highconcentration of conduction electrons and correlates with the large value of themagnetic-field-induced strain observed in the alloys of such composition. The temperaturedependence of the skin layer depth is found from the sharp decay of the CESR signal withtemperature, which is related to the disappearing large magnetic resistance aftertransformation to the paramagnetic state.