Tuning of Conventional and Inverse Magnetocaloric Effect Coexistence in Ge‐Modified MnZnSb Single Crystal

The magnetic properties of MnZnSb x Ge 1− x single crystals ( x = 0, 0.05, 0.10, and 0.15) are systematically studied to explore their magnetocaloric behavior. All compositions exhibit a paramagnetic‐to‐ferromagnetic transition near room temperature. A notable magnetic‐field‐induced first‐order magnetic phase transition is observed at ≈155 K ( T t ) for x = 0.05, accompanied by a hysteresis width of ≈9 K, attributed solely to Ge substitution at Sb sites. The magnetic entropy change (Δ S M ( T , H )), calculated using the Maxwell relation at the Curie temperature ( T C ≈ 315 K), is −0.55 J kg − 1 K − 1 for x = 0 and −0.49 J kg − 1 K − 1 for x = 0.05 under a 1.2 T field, indicating a conventional magnetocaloric effect. Interestingly, for x = 0.05 at T t ≈ 155 K, Δ S M ( T , H ) reaches +0.22 J kg − 1 K − 1 , marking an inverse magnetocaloric effect due to magnetic phase coexistence and structural coupling. To support the experimental observations, the magnetic entropy change Δ S M ( T , H ) is theoretically analyzed using Landau theory, and critical parameters are determined to identify the nature of magnetic interactions driving the transition. These results on dual‐action capability make MnZnSb x Ge 1− x a highly promising candidate for next‐generation magnetic refrigeration technologies.