Magnetic, magnetocaloric effect and resistivity behavior of Sb substituted MnAs

Highlights: • MnAs_1−xSb_x systems exhibit ferromagnetic to paramagnetic transition for x ≤ 0.3. • The first order transition temperature T_C monotonically decreases with composition. • System exhibit metal to insulator transition at T_C. • Magnetic entropy change(ΔS) is independent of studied four measurement protocols. • Lattice elongation is responsible for decrease in T_C and Debye temperature Θ_D. -- Abstract: Magnetic, magnetocaloric effect and resistivity behavior of phase pure MnAs_1−xSb_x systems, synthesized by solid state reaction, have been studied for x up to 0.3. The systems display ferromagnetic metal to paramagnetic insulator transition and the transition temperature T_C systematically decreases with increase in x. Arrot plot analysis indicate that the magnetic transition is of first order for all the samples though thermal hysteresis about T_C is observed only for x up to 0.15. Isothermal magnetization measurements have been performed in four different protocols traversing distinctive thermodynamic paths and the isothermal magnetic entropy changes (ΔS) have been estimated using Maxwell thermodynamic equation. ΔS(T) exhibit similar asymmetric peak behavior for samples in the range 0.1–0.3 about the corresponding T_C both in shape and magnitude, where as x = 0.05 sample exhibits sharp peak followed by a plateau for field change ΔH in the range 10–70 kOe. The value of extracted ΔS(T) is independent of the measurement protocol within the estimated error for all the samples. The calculated refrigeration capacity for two considered cases of hot and cold sink temperatures, viz. T_C – 25 and T_C + 25 K and temperatures at the full width half maximum is found to be same in all the samples for any ΔH in the range 10–70 kOe. Resistivity behavior in ferromagnetic region manifests contribution from electron-magnon scattering following T² dependence and electron-phonon contribution following Bloch-Grüneisen formalism. Our analysis indicates lattice elongation is responsible for reduction in T_C and Debye temperature Θ_D. It is surmised that enhanced spin fluctuations are responsible for paramagnetic insulating behavior.