The critical exponents provide important information concerning the interaction mechanisms near the paramagnetic-to-ferromagnetic transition. In this paper, we present a thorough study of the critical behavior of a La 0.9Pb 0.1MnO 3 polycrystalline sample by analyzing isothermal magnetization data. We determined the Curie temperature (T=162 K) and the critical exponents ( β=0.498, γ=1.456, and δ=3.92). With these exponents, we could successfully fit the scaling equation of state M(H,∊)=∊βf±(H/∊), where ∊=(T-T)/T, f+ for T>T and f- for T<T are regular scaling functions. We found that, at T<T, β was close to the predicted value for the mean-field theory, whereas the value for γ was close to that for the Heisenberg model. We conjecture this feature originates from ferromagnetic clusters existing at wide ranging temperatures including even above TC. This conjecture was confirmed by electron paramagnetic resonance spectra around the Curie temperature.
Journal of Magnetism and Magnetic Materials
- Pub Date:
- September 2006
- Static properties;
- Equilibrium properties near critical points critical exponents;
- Electron paramagnetic resonance and relaxation