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Magnetoresistance of a Dilute Ferromagnetic PdMn Alloy: Acoustic- and Optic-Mode Excitations,
SUSSEX UNIV BRIGHTON (ENGLAND) SCHOOL OF MATHEMATICAL AND PHYSICAL SCIENCES
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Magnetoresistance measurements on a Pd-2.91-at. Mn alloy in the temperature range 1.4-20K and in applied fields up to 60 kOe are presented. The data demonstrate the effects of interimpurity near-neighbor covalent admixture, the antiferromagnetic coupling from which appears to be in qualitative agreement with the calculations of Moriya. These data also allow an estimate of the near-neighbor Mn-Mn interaction energy to be made, and this is compared with quantitative estimates on the basis of the double-resonance coupling mechanism of Caroli and Blandin. By including a magnetic field in the collective-excitation model of Long and Turner, the magnetoresistance data can be fitted once allowance has been made for near-neighbor antiferromagnetic coupling. The acoustic-spin-wave stiffness D, which is obtained by fitting the data to this model, is found to be field dependent it decreases rapidly with increasing field. The possibility of optical-mode collective excitations is briefly discussed. Author
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