Experimental realization of helical magnetic structure at Ni/Gd interfaces at room temperature

Abstract

Rare earth (RE) metal in proximity with transition metal (TM) normally exhibits a strong antiferromagnetic exchange interaction and thus reveals an increase in the curie temperature of RE and twisted magnetic structures. Here, we measured depth profiling of the structure and magnetic properties of Ni/Gd multilayer at room temperature using polarized neutron reflectivity (PNR), suggesting intermixing and long-range ordered magnetism at interfaces. We observed different spin-dependent PNR profiles from the multilayer on reflecting neutrons from front and back surfaces. The analysis of the observed PNR profiles can be explained by the twisted magnetic phase at interfaces due to strong antiferromagnetic exchange interaction between Ni (TM) and Gd (RE). Diffuse PNR measurements indicate that the structural and magnetic roughnesses at the interfaces are not correlated. The depth-dependent experimental techniques were supported by a simple one-dimensional (1D) spin-based model calculation for the existence of a magnetic helical (twisted) phase at the interfaces in this system at room temperature. The twisted phase may be contributing significantly to modifying the temperature-dependent magnetic properties. This work demonstrates the realization of a twisted phase at room temperature in the RE/TM system, paving a pathway to manipulate the magnetic properties for all-optical electronics for future magnetic memory applications.