Ferromagnetic Resonance in Nickel and in some of its Alloys

Abstract

From microwave resonance measurements, g values and line widths for nickel and for Ni-Cu, Ni-Al, Ni-Sb and Ni-Mn alloys with high nickel content have been determined. Measurements were made at a wavelength of 1 22 cm and usually in the temperature range 20-200°C. A constant temperature independent g value of 2.19 ± 0.02 was found for all specimens except the Ni-Mn alloys; for these a decrease in g value with increase in manganese content occurred, reaching 2.11 for the 13.5 atomic per cent Mn alloy. An explanation of this behaviour is given. Absolute absorption measurements were made and the line widths are expressed in terms of the damping constant 1/T₂ introduced by Bloembergen (1950). For a given alloy the shape of the curve of 1/T₂ against reduced temperature is similar to that found by Bloembergen for nickel but varies from alloy to alloy. A single curve of exponential form is found to represent the results when 1 T₂ is plotted against saturation intensity of magnetization M, an increase in 1 T₂ accompanying a decrease in M. A possible explanation is qualitatively presented.