⁵⁷Fe Mössbauer studies of amorphous Pd₄₀(NiFe)₄₀P₂₀ alloys

Abstract

Zero-field ⁵⁷Fe Mössbauer spectroscopy has been used to study the magnetic properties of an amorphous melt–spun Pd₄₀Ni_40−x Fe _x P₂₀ (x = 5, 10, 17.5, 20) series. The alloys show quadrupole split doublets at room temperature indicating paramagnetic behaviour. At low temperatures the Mössbauer spectra are sextets due to the onset of long range order. The transition temperatures increase with Fe concentration from 12 ± 2 K for Pd₄₀Ni₃₅Fe₅P₂₀ to 42.0 ± 2.0 K for Pd₄₀Ni₂₀Fe₂₀P₂₀. The hyperfine field was found to follow ${\text{Hf}}{\left( {\text{0}} \right)}{\left( {{\text{1 - }}T \mathord{\left/ {\vphantom {T {T_{{\text{c}}} }}} \right. \kern-\nulldelimiterspace} {T_{{\text{c}}} }} \right)}^{{\text{ $ \beta $ }}}$ over the critical region with the β exponent being close to 0.4.