Films*

Electrolyte gating techniques have proven remarkably effective in the study of charge density effects in a variety of conductors. The ability to controllably induce surface charge densities > 10¹⁴ cm^-2 has led to their extensive use in the study of superconductivity, insulator-metal transitions, and magnetism. In this work we apply electrolyte gating to epitaxial films of La_1-xSr_xCoO_3-δ (LSCO), seeking gate-control of ferromagnetism. Our previous work provided direct evidence of oxygen vacancy creation at positive bias, vs. electrostatic hole accumulation at negative bias, using transport as well as in operando X-ray synchrotron and polarized neutron reflectometry (PNR) measurements [1]. Here, we present detailed gate-control over resistivity, magnetoresistance, magnetization, and Curie temperature under hole accumulation, including gate-induced ferromagnetism verified by PNR. These are discussed in terms of recently developed theory for electrolyte-gate-induced percolation [2].
[1] Walter et al., ACS Nano 10, 7799 (2016). Walter et al., Phys. Rev. Mater., under review (2017).
[2] Orth et al., Phys. Rev. Lett. 118, 106801 (2017)