Overcoming the metamagnetic phase transition by epitaxial strain and its impact on magnetocaloric effect in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>Dy</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub>

Rare-earth-based double perovskites exhibit a large magnetocaloric effect, but often undergo first-order magnetic transitions because of the field-induced metamagnetic behavior. Since the first-order transitions involve a large hysteresis loss in a cooling cycle, suppression of the metamagnetic behavior is essential to improve the efficiency of such double perovskites. A promising approach for negating the loss of hysteresis involves modulating strain-sensitive magnetic interactions via thin films. In this work, we demonstrate that epitaxial strain significantly suppresses the metamagnetic behavior in epitaxial ${\mathrm{Dy}}_{2}{\mathrm{NiMnO}}_{6}$ grown on ${\mathrm{SrTiO}}_{3}$ and ${\mathrm{LaAlO}}_{3}$ compared to its bulk counterpart. Such epitaxial strain modifies the magnetic transition from the first order in bulk to the second order in thin films and significantly impacts the magnetocaloric properties. This difference is primarily attributed to strain-induced modifications in the Dy-(Ni/Mn) exchange interactions, driven by changes in the Ni-Mn exchange strength. Density functional theory calculations further confirm the role of strain in modifying the exchange interaction. Manipulating the order of magnetic phase transitions via strain engineering opens up the possibility of enhancing the magnetocaloric cooling efficiency in double perovskites and other first-order transition materials.