Surface and bulk characterization of magnetic multilayers formed within a single layer FeRh by hydrogen ion irradiation

In modern spintronics, magnetic multilayers, such as a ferromagnet/antiferromagnet (FM/AFM) heterostructure, are essential for achieving novel and practical capabilities, including the exchange bias effect, spin-transfer torque, tunneling magnetoresistance, etc. As these functions are determined by the exchange interaction or the carrier transport across the interface, it is critical to optimize the magnetic interface usually formed between different materials with the chemical mismatch as well as the structural discontinuity. Here, we explored the potential of FeRh for creating the FM/AFM multilayer within a single material by exploiting its tunability of the temperature-dependent AFM-FM transition with a hydrogen ion irradiation. We investigated bulk and surface magnetic states separately based on a magneto-optical Kerr effect and magnetization-induced second-harmonic generation, respectively, and could reveal that FeRh can host the FM (surface)/AFM (bulk) magnetic multilayer within a single layer of FeRh even at room temperature prepared with a hydrogen ion dose of 2.0×1015 H+/cm2. As the FM and AFM states are stabilized with a well-defined spatial separation as manifested by the exchange bias effect, we expect the FeRh-based FM/AFM bilayer to alleviate limitations arising from the interfaces formed by otherwise different materials. [Display omitted] •Magnetic properties of the surface and bulk of FeRh were separately investigated using MSHG and MOKE techniques.•During temperature-dependent magnetic phase transitions, the surface and the bulk exhibit distinct magnetic characteristics.•Exchange bias field was confirmed for the surface FM state originating from its interaction with the bulk AFM state.•FM/AFM multilayer structure is realized at room temperature for the hydrogen-ion irradiated FeRh films.