Abstract
Dissipation-less electric control of magnetic state variable is an important target of contemporary spintronics. The non-volatile control of magnetic skyrmions, nanometre-sized spin-swirling objects, with electric fields may exemplify this goal. The skyrmion-hosting magnetoelectric chiral magnet Cu2OSeO3 provides a unique platform for the implementation of such control; however, the hysteresis that accompanies the first-order transition associated with the skyrmion phase is negligibly narrow in practice. Here we demonstrate another method that functions irrespective of the transition boundary. Combination of magnetic-susceptibility measurements and microwave spectroscopy reveals that although the metastable skyrmion lattice is normally hidden behind a more thermodynamically stable conical phase, it emerges under electric fields and persists down to the lowest temperature. Once created, this metastable skyrmion lattice remains without electric fields, establishing a bistability distinct from the transition hysteresis. This bistability thus enables non-volatile electric-field control of the skyrmion lattice even in temperature/magnetic-field regions far from the transition boundary.
Highlights
Dissipation-less electric control of magnetic state variable is an important target of contemporary spintronics
The more thermodynamically stable state should be interchanged when positive and negative external fields are applied. These two requirements are always satisfied in the hysteresis region of a first-order transition; the hysteresis of the transition between the skyrmion phase and another magnetic order is too narrow in width to be observed in the magnetoelectric Cu2OSeO3, the first requirement is not fulfilled in practice with regard to this conventional hysteresis
We first address how the thermodynamic stability of the skyrmion phase varies under electric fields by measuring the a.c. susceptibility w0 as a sensitive probe for skyrmion formation8,21
Summary
Dissipation-less electric control of magnetic state variable is an important target of contemporary spintronics. Combination of magnetic-susceptibility measurements and microwave spectroscopy reveals that the metastable skyrmion lattice is normally hidden behind a more thermodynamically stable conical phase, it emerges under electric fields and persists down to the lowest temperature Once created, this metastable skyrmion lattice remains without electric fields, establishing a bistability distinct from the transition hysteresis. Combination of magnetic-susceptibility measurement and microwave spectroscopy reveals that metastable skyrmion lattice is potentially hidden behind the conical phase and can be created by applying electric fields Once created, this metastable state remains even without the electric field, establishing bistability even far from the phase boundary. This metastable state remains even without the electric field, establishing bistability even far from the phase boundary By controlling both thermodynamic stability and metastability, the skyrmion lattice can be created and annihilated with electric fields isothermally, realizing non-volatile switching. This finding can lead to conceptually new guiding principle of non-volatile skyrmion phase control that is applicable to other external stimuli
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