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Magnetic properties of amorphous (formula presented) alloys
A. Perumal, , K.S. Kim, S.C. Yu, V.V. Rao, R.A. Dunlap
Published in
2002
Volume: 65
   
Issue: 6
Pages: 1 - 15
Abstract
The magnetization as a function of field and temperature has been measured for a series of amorphous (formula presented) alloys with (formula presented) in the temperature range 4.2-300 K. All the samples of the present study show double transition (reentrant) behavior below room temperature. The high-temperature transition (formula presented) decreases linearly at about 6 K/at. % of Mn, while the low-temperature transition (formula presented) increases at about 2.6 K/at. % of Mn. A detailed analysis of the temperature dependence of magnetization data reveals: (i) Spin-wave excitations at low-temperature, single-particle excitations and local-spin-density fluctuations (LSDF’s) over a wide range of intermediate temperatures and enhanced fluctuations in the local magnetization for temperature close to (formula presented) contribute dominantly to the thermal demagnetization of spontaneous magnetizations; (ii) external applied magnetic field of strength (formula presented) suppresses the LSDF’s; (iii) the spin-wave stiffness constant (D) decreases from (formula presented) to (formula presented) with increasing Mn concentration; and (iv) the (formula presented) ratio remains constant for all the compositions. A study of critical behavior of the magnetic order-disorder transition by various methods suggest that the critical exponents obtained below and above Curie temperature obey a scaling law (formula presented) and (formula presented) with a high degree of accuracy in the asymptotic critical region. The exponents are independent of composition and are in close agreement with the values those predicted for three-dimensional Heisenberg ferromagnets. The magnetic parameters such as high-field susceptibility, coercivity, local magnetic anisotropy, and spin-glass behavior, obtained from the low-temperature magnetization data, are consistent with the presence of a mixed magnetic state. The detailed analysis of high-field thermomagnetization data could be explained in terms of the nearest-neighbor Heisenberg model. Moreover, the temperature dependence of the magnetic behavior is discussed in terms of competing ferromagnetic and antiferromagnetic exchange interactions. © 2002 The American Physical Society.
About the journal
JournalPhysical Review B - Condensed Matter and Materials Physics
ISSN10980121