# Focused ion beam direct writing of magnetic patterns with controlled structural and magnetic properties

## TL;DR

This paper demonstrates how focused ion beam irradiation can precisely create magnetic patterns with tailored structural and magnetic properties in FeNi thin films, enabling rapid prototyping of complex magnonic devices.

## Contribution

It introduces a method to control phase transformation and magnetic anisotropy in FeNi films using focused ion beam parameters, allowing customizable magnetic nanostructures.

## Key findings

- Controlled phase transformation from fcc to bcc achieved.
- Magnetic anisotropy can be switched from four-fold to uniaxial.
- Patterned magnetic structures suitable for magnonic applications.

## Abstract

Focused ion beam irradiation of metastable Fe$_{78}$Ni$_{22}$ thin films grown on Cu(100) substrates is used to create ferromagnetic, body-centered-cubic patterns embedded into paramagnetic, face-centered-cubic surrounding. The structural and magnetic phase transformation can be controlled by varying parameters of the transforming gallium ion beam. The focused ion beam parameters as ion dose, number of scans, and scanning direction can be used not only to control a degree of transformation, but also to change the otherwise four-fold in-plane magnetic anisotropy into the uniaxial anisotropy along specific crystallographic direction. This change is associated with a preferred growth of specific crystallographic domains. The possibility to create magnetic patterns with continuous magnetization transitions and at the same time to create patterns with periodical changes in magnetic anisotropy makes this system an ideal candidate for rapid prototyping of a large variety of nanostructured samples. Namely spin-wave waveguides and magnonic crystals can be easily combined into complex devices in a single fabrication step.

---
Source: https://tomesphere.com/paper/1803.04348