# Tunability of Room Temperature Ferromagnetism in Spintronic Semiconductors through Non-magnetic Atoms

## TL;DR

This study demonstrates how adding non-magnetic aluminum atoms to nickel ferrite can precisely tune its room temperature ferromagnetism without significantly affecting its electronic properties, advancing magnetic semiconductor technology.

## Contribution

First to show that non-magnetic aluminum can control RTFM in nickel ferrite by site-specific occupancy, enhancing material versatility for spintronic applications.

## Key findings

- Aluminum inclusion allows selective tuning of iron site occupancies.
- The magnetic properties can be controlled without altering electronic structure.
- The material retains electronic properties while achieving desired magnetic behavior.

## Abstract

The implementation and control of room temperature ferromagnetism (RTFM) by adding magnetic atoms to a semiconductor's lattice has been one of the most important problems in solid state state physics in the last decade. Herein we report for the first time, to our knowledge, on the mechanism that allows RTFM to be tuned by the inclusion of \emph{non-magnetic} aluminum in nickel ferrite. This material, NiFe$_{2-x}$Al$_x$O$_4$ (x=0, 0.5, 1.5), has already shown much promise for magnetic semiconductor technologies, and we are able to add to its versatility technological viability with our results. The site occupancies and valencies of Fe atoms (Fe$^{3+}$ T$_d$, Fe$^{2+}$ O$_h$, and Fe$^{3+}$ O$_h$) can be methodically controlled by including aluminum. Using the fact that aluminum strongly prefers a 3+ octahedral environment, we can selectively fill iron sites with aluminum atoms, and hence specifically tune the magnetic contributions for each of the iron sites, and therefore the bulk material as well. Interestingly, the influence of the aluminum is weak on the electronic structure (supplemental material), allowing one to retain the desirable electronic properties while achieving desirable magnetic properties.