Type-I Multiferroic VHfO$_4$ with Strain-Switchable Magnetic Orders and Magnetoelectric Coupling

TL;DR

This paper proposes VHfO$_4$, a new multiferroic oxide with strain-tunable magnetic and electric properties, combining ferroelectricity and magnetism for potential spintronics applications.

Contribution

It introduces VHfO$_4$ as a novel Type-I multiferroic with coexisting ferroic orders and demonstrates strain-controlled magnetic states through first-principles and Monte Carlo simulations.

Findings

VHfO$_4$ exhibits stable ferroelectric polarization and magnetism.

Strain engineering enables switching between multiple magnetic states.

Magnetic properties can be controlled via $c$-axis strain.

Abstract

Motivated by the complementary properties of vanadium-based ferromagnets and HfO$_2$-based ferroelectrics, we propose a novel multiferroic oxide, VHfO$_4$, through 50\% Hf$^{4+}$ substitution with V$^{4+}$ in the ferroelectric $Pca2_1$ phase of HfO$_2$. First-principles DFT calculations reveal that the $Pca2_1$-like VHfO$_4$ phase exhibits dynamic stability and concurrent ferroic orders: robust ferroelectric polarization comparable to HfO$_2$ and V-driven magnetism. Parallel tempering Monte Carlo simulations identify an antiferromagnetic ground state, while strain engineering enables tunable magnetoelectric coupling. Biaxial in-plane strain induces four magnetic states: intralayer FM/interlayer AFM, intralayer AFM/interlayer FM, spiral-like non-collinear order, and discrete alternating spin alignment. Critically, $c$-axis strain modulates magnetic energy landscapes, demonstrating electromechanical control of magnetism. This work establishes VHfO$_4$ as a Type-I multiferroic with coexisting atomic-scale ferroic origins and strain-tunable cross-coupling, offering a platform for voltage-controlled spintronics devices.