Controlling magnetism with electric field directly or through strain-driven piezoelectric coupling remains a key goal of spintronics. Here, we demonstrate that giant piezomagnetism, a linear magneto-mechanic coupling effect, is manifest in antiperovskite MnNiN, facilitated by its geometrically frustrated antiferromagnetism opening the possibility of new memory device concepts. Films of MnNiN with intrinsic biaxial strains of ±0.25% result in Néel transition shifts up to 60 K and magnetization changes consistent with theory. Films grown on BaTiO display a striking magnetization jump in response to uniaxial strain from the intrinsic BaTiO structural transition, with an inferred 44% strain coupling efficiency and a magnetoelectric coefficient α (where α = d B/d E) of 0.018 G cm/V. The latter agrees with the 1000-fold increase over CrO predicted by theory. Overall, our observations pave the way for further research into the broader family of Mn-based antiperovskites where yet larger piezomagnetic effects are predicted to occur at room temperature.

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Multicomponent magnetic phase diagrams are a key property of functional materials for a variety of uses, such as manipulation of magnetization for energy efficient memory, data storage, and cooling applications. Strong spin-lattice coupling extends this functionality further by allowing electricfield-control of magnetization via strain coupling with a piezoelectric. Here this work explores the magnetic phase diagram of piezomagnetic Mn 3 NiN thin films, with a frustrated noncollinear antiferromagnetic (AFM) structure, as a function of the growth induced biaxial strain. Under compressive strain, the films support a canted AFM state with large coercivity of the transverse anomalous Hall resistivity, ρ xy , at low temperature, that transforms at a welldefined Néel transition temperature (T N ) into a soft ferrimagnetic-like (FIM) state at high temperatures. In stark contrast, under tensile strain, the low temperature canted AFM phase transitions to a state where ρ xy is an order of magnitude smaller and therefore consistent with a low magnetization phase. Neutron scattering confirms that the high temperature FIM-like phase of compressively strained films is magnetically ordered and the transition at T N is first-order. The results open the field toward future exploration of electricfield-driven piezospintronic and thin film caloric cooling applications in both Mn 3 NiN itself and the broader Mn 3 AN family.

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