Electron Spin Resonance in Ferromagnetic Sc3+xIn Alloys

Abstract

We report the observation of electron spin resonance (ESR) in ferromagnetic Sc_3+xIn. This material shows a strong narrow peak in the total magnetization as a function of x, with ferromagnetism occurring at low temperatures for x in the range of 0.10–0.20. We have studied the ESR properties of thin polycrystalline plates for several values of x lying both within and also outside the ferromagnetic region. Measurements were made at 12 and 18 GHz as a function of temperature. The temperature range extended from 1.3 to 50 K (several times the maximum Curie temperature, T_c, of 7 K). The g‐value (corrected for demagnetization effects) is 2.02±0.01 at 1.4 K and appears to decrease to approximately 1.99 at the highest observable temperatures. The minimum linewidth occurs at T_c and increases slightly at lower temperatures. For T>T_c the line broadens rapidly with increasing temperatures. A comparison of the ESR linewidth with the reciprocal of the total magnetization as a function of temperature shows that even though both have the same qualitative type of behavior, the quantitative agreement is not as good as that predicted by the theory of exchange enhancement of spin lifetimes. Although one might normally expect a rather fast relaxation rate for the electrons of such an alloy, it appears that the small g‐shift and a form of exchange enhancement are important for substantially increasing spin lifetimes and producing narrow lines at low temperatures.