Magnetic properties of amorphous Fe90-xMnxZr10(0≤x≤12) alloys -: art. no. 064428

The magnetization as a function of field and temperature has been measured for a series of amorphous Fe90-xMnxZr10 alloys with x = 0-12 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 (T-c) decreases linearly at about 6 K/at. % of Mn, while the low-temperature transition (T-ve) 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 T-c contribute dominantly to the thermal demagnetization of spontaneous magnetizations: (ii) external applied magnetic field of strength greater than or equal to5 kOe suppresses the LSDF's: (iii) the spin-wave stiffness constant (D) decreases from 35.6+/-0.3 to 23.2+/-0.2 meV Angstrom(2) with increasing Mn concentration: and (iv) the D/T-c 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 [delta-1 = gamma/beta and alpha + gamma = 2(1 - beta)] 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 anti ferromagnetic exchange interactions.