title: Robust metastable skyrmions and their triangular-square lattice structural transition in a high-temperature chiral magnet.
abstract: Skyrmions, topologically protected nanometric spin vortices, are being investigated extensively in various magnets. Among them, many structurally chiral cubic magnets host the triangular-lattice skyrmion crystal (SkX) as the thermodynamic equilibrium state. However, this state exists only in a narrow temperature and magnetic-field region just below the magnetic transition temperature Tc, while a helical or conical magnetic state prevails at lower temperatures. Here we describe that for a room-temperature skyrmion material, β-Mn-type Co8Zn8Mn4, a field-cooling via the equilibrium SkX state can suppress the transition to the helical or conical state, instead realizing robust metastable SkX states that survive over a very wide temperature and magnetic-field region. Furthermore, the lattice form of the metastable SkX is found to undergo reversible transitions between a conventional triangular lattice and a novel square lattice upon varying the temperature and magnetic field. These findings exemplify the topological robustness of the once-created skyrmions, and establish metastable skyrmion phases as a fertile ground for technological applications.
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: K
authors.identifier: http://orcid.org/0000-0002-0382-895X
authors.initials: K
authors.lastname: Karube
authors.affiliation: Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors.forename: J S
authors.identifier: http://orcid.org/0000-0001-7738-0150
authors.initials: JS
authors.lastname: White
authors.affiliation: Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.|Laboratory for Quantum Magnetism (LQM), Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: N
authors.initials: N
authors.lastname: Reynolds
authors.affiliation: Laboratory for Neutron Scattering and Imaging (LNS), Paul Scherrer Institute (PSI), CH-5232 Villigen, Switzerland.
authors.forename: J L
authors.initials: JL
authors.lastname: Gavilano
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: H
authors.initials: H
authors.lastname: Oike
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: A
authors.initials: A
authors.lastname: Kikkawa
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: F
authors.identifier: http://orcid.org/0000-0002-1763-6799
authors.initials: F
authors.lastname: Kagawa
authors.affiliation: Department of Advanced Materials Science, University of Tokyo, Kashiwa 277-8561, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tokunaga
authors.affiliation: Laboratory for Quantum Magnetism (LQM), Institute of Physics, École Polytechnique Fédérale de Lausanne (EPFL), CH-1015 Lausanne, Switzerland.
authors.forename: H M
authors.identifier: http://orcid.org/0000-0002-8832-8865
authors.initials: HM
authors.lastname: Rønnow
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.|Department of Applied Physics, University of Tokyo, Bunkyo-ku 113-8656, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Tokura
authors.affiliation: RIKEN Center for Emergent Matter Science (CEMS), Wako 351-0198, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Taguchi