Strain and magnetic properties of antiferromagnetic NaNiF3 thin films*

Fluoro-perovskites have been proposed as an alternative candidate to the oxide perovskites for magneto-electric applications.^{1 ,2} It is therefore desirable to create thin film samples to integrate into devices. NaNiF3 (NNF) is an antiferromagnet which has a distorted perovskite crystal structure that sustains weak ferromagnetism with a bulk T_N = 156 K and a Pnma space group symmetry.³ We have grown NNF via molecular beam epitaxy on SrTiO3 (100) to produce high quality epitaxial films in the thickness range of 5- 50 nm. The films had the expected the Pnma structure and were predominantly oriented along the [101] direction. The SQUID magnetometry displayed a temperature-dependent magnetization consistent with antiferromagnetic ordering and a weak ferromagnetic moment. We observe a thickness-dependent transition temperature, where the change is ΔT_N = -7 K for decreasing thickness between 40 and 10 nm, which correlates with the increased tensile strain measured using x-ray diffraction.
[1] A. KC et al., Appl. Phys. Lett. 110, 92901 (2017).
[2] M. Yang et al., Sci. Rep. 7 7182 (2017).
[3] V. M. Judin and A. B. Sherman, Phys. Stat. Sol. 20 759 (1967).