Magnetic Yoking and Tunable Interactions in FePt-Based Hard/Soft Bilayers

TL;DR

This paper demonstrates a highly sensitive magnetic yoking effect and tunable interactions in FePt-based bilayers, enabling precise control of magnetic coupling for advanced nanomagnetic and spintronic applications.

Contribution

It reveals how the soft layer mediates exchange and dipolar interactions in FePt bilayers, with experimental and simulation validation, offering a new approach to control magnetic interactions.

Findings

Soft layer mediates exchange coupling below exchange length.

Thicker soft layer induces in-plane yoking of dipolar fields.

Experimental and simulation methods confirm the interaction evolution.

Abstract

Assessing and controlling magnetic interactions in magnetic nanostructures are critical to nanomagnetic and spintronic explorations, such as magnetic recording media, permanent magnets, magnetic memory and logic devices, etc. Here we demonstrate an extremely sensitive magnetic yoking effect and tunable interactions in FePt based hard/soft bilayers mediated by the soft layer. Below the exchange length, a thin soft layer strongly exchange couples to the perpendicular moments of the hard layer; above the exchange length, just a few nanometers thicker, the soft layer moments turn in-plane and act to yoke the dipolar fields from the adjacent hard layer perpendicular domains. The evolution from exchange to dipolar-dominated interactions is experimentally captured by first-order reversal curves, the delta-M method, and polarized neutron reflectometry, and confirmed by micromagnetic simulations. These findings demonstrate an effective yoking approach to design and control magnetic interactions in wide varieties of magnetic nanostructures and devices.