<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:mrow> <mml:msub> <mml:mi>La</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi mathvariant="normal">O</mml:mi> <mml:mn>3</mml:mn> </mml:msub> <mml:msub> <mml:mi>Mn</mml:mi> <mml:mn>2</mml:mn> </mml:msub> <mml:msub> <mml:mi>Se</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:mrow> </mml:math> : A correlated insulating layered <i>d</i> -wave altermagnet
Cheng-Fu Wei, Xiaoyin Li, Sabrina Hatt, Xudong Huai, Jue Liu, Birender Singh, Kyung-Mo Kim, Rafael M. Fernandes, Paul Cardon, Liuyan Zhao, T. Thao Tran, Benjamin A. Frandsen, Kenneth S. Burch, Feng Liu, Huiwen Ji
Abstract
Altermagnets represent a new class of magnetic phases without net magnetization, invariant under a combination of rotation and time reversal. Unlike conventional collinear antiferromagnets (AFM), altermagnets could lead to new correlated states and important material properties deriving from their nonrelativistic spin-split band structure. Indeed, they serve as the magnetic analogue of unconventional superconductors and can yield spin-polarized electrical currents in the absence of external magnetic fields, making them promising candidates for next-generation spintronics. Here, we report altermagnetism in the correlated insulator, magnetically ordered tetragonal oxychalcogenide, $\mathrm{L}{\mathrm{a}}_{2}{\mathrm{O}}_{3}\mathrm{M}{\mathrm{n}}_{2}\mathrm{S}{\mathrm{e}}_{2}$. Symmetry analysis reveals a ${d}_{{x}^{2}\ensuremath{-}{y}^{2}}$-wave-like spin-momentum locking arising from the $\mathrm{M}{\mathrm{n}}_{2}\mathrm{O}$ Lieb lattice, supported by density functional theory (DFT) calculations. Magnetic measurements confirm the AFM transition below $\ensuremath{\sim}166\phantom{\rule{0.16em}{0ex}}\mathrm{K}$ while neutron pair distribution function analysis reveals a 2D short-range magnetic order that persists above the N\'eel temperature. Single crystals are grown and characterized using x-ray diffraction, optical and electron microscopy, and micro-Raman spectroscopy to confirm the crystal structure, stoichiometry, and uniformity. Our findings establish $\mathrm{L}{\mathrm{a}}_{2}{\mathrm{O}}_{3}\mathrm{M}{\mathrm{n}}_{2}\mathrm{S}{\mathrm{e}}_{2}$ as a model altermagnetic system realized on a Lieb lattice.