We report magnetic behavior of a dilute ferromagnetic alloy Ni1−xMnx, 0<x<25%. Magnetic circular dichroism (MCD) is used to examine the local magnetic moment on each element, and superconducting quantum interference device magnetometry is used to evaluate the magnetization of the alloy as a whole. Both MCD and hysteresis loops show a collapse in moment at x≈15% measured at 100 K. The Mn doping appears to disturb the long-range ordering of the host nickel spins which, in the concentration range studied, is a precursor disordered ferromagnet prior to a spin-glass phase.
We report an analysis of data on the thickness-dependent Curie temperatures TC of itinerant ferromagnetic thin films with variable range of spin interactions “tuned” by alloying transition metals. We observe that TC decreases with decreasing film thickness according to the finite-size effect power law for two-dimensional Ising thin films, down to a critical thickness R0, beyond which point TC reduces linearly with further decreasing thickness. The demarcation point scales with the range of spin interactions R0. The parameter R0 scales with the evolution of the magnetic moment on the Slater-Pauling curve. This analysis of ultrathin film data provides a measure of the effective range of spin interactions in ferromagnets and demonstrates that, when the dimension L reduces below the intrinsic interaction length R0, TC no longer follows the finite-size effect power law behavior.
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