摘要：The applicability of magnetocaloric materials is limited by irreversibility. In this work, we evaluate the reversible magnetocaloric response associated with magnetoelastic transitions in the framework of the Bean-Rodbell model. This model allows the description of both second- and first-order magnetoelastic transitions by the modification of the <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mi>η</mi></semantics></math></inline-formula> parameter (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo><</mo><mn>1</mn></mrow></semantics></math></inline-formula> for second-order and <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo>></mo><mn>1</mn></mrow></semantics></math></inline-formula> for first-order ones). The response is quantified via the Temperature-averaged Entropy Change (<inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>T</mi><mi>E</mi><mi>C</mi></mrow></semantics></math></inline-formula>), which has been shown to be an easy and effective figure of merit for magnetocaloric materials. A strong magnetic field dependence of <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>T</mi><mi>E</mi><mi>C</mi></mrow></semantics></math></inline-formula> is found for first-order transitions, having a significant increase when the magnetic field is large enough to overcome the thermal hysteresis of the material observed at zero field. This field value, as well as the magnetic field evolution of the transition temperature, strongly depend on the atomic magnetic moment of the material. For a moderate magnetic field change of 2 T, first-order transitions with <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>η</mi><mo>≈</mo><mn>1.3</mn><mo>−</mo><mn>1.8</mn></mrow></semantics></math></inline-formula> have better <inline-formula><math xmlns="http://www.w3.org/1998/Math/MathML" display="inline"><semantics><mrow><mi>T</mi><mi>E</mi><mi>C</mi></mrow></semantics></math></inline-formula> than those corresponding to stronger first-order transitions and even second-order ones.
