Realization of noncollinear spin structure in Zn/Al-doped nickel ferrite: Understanding the role of Zn dopant

Realization of noncollinear spin structures together with low-damping has been remained challenging so far. Ferrimagnetic Zn/Al-substituted nickel ferrite (Ni0.65Zn0.35Al0.8Fe1.2O4; NiZAF) has recently been proposed as an excellent choice for low-damping spintronics. However, realization of noncollinear spin-structure is lacking so far in NiZAF. Our recent combined study of synchrotron XMCD and XRMR in addition to the lab-based characterizations for the Dy-doped NiZAF ultrathin film revealed spiral-type noncollinear spin-structure. The Dy-L3 EXAFS and theoretical calculations revealed such noncollinearity in Dy-doped NiZAF is stabilized through DMI induced by a local strain created by the larger Dy cation. However, our recent SQUID results hint for noncollinearity even in the pristine NiZAF. This raises a natural question: does the noncollinearity in the pristine NiZAF occur due to Zn itself via local distortion, or can it persist even without any Zn? For this end, our aim is to measure XMCD and XRMR to address the mechanism of noncollinearity and type of magnetic profile in the NiZAF thin films with varying Zn content and thickness. This study is essential to better understand and design the noncollinear spinel-ferrites for oxide-based spintronics.