Quantum Matter Seminar

Abstract

Geometrically frustrated systems have an inherent incompatibility between the lattice geometry and the magnetic interactions, resulting in macroscopically degenerate ground-state manifolds. The single-ion anisotropy and magnetic interactions in spin-ice systems give rise to unusual non-collinear spin textures, such as Pauling states and emergent quasiparticle excitations equivalent to magnetic monopoles. The effective spin correlation strength (Jeff) determines the relative energies of the different spin-ice states and the magneto-chemical potential (MCP) associated with monopole formation. There is an enticing potential of using these monopoles for the development of new quantum information applications. To realize this, thin films are required. The thin films in my group are grown using pulsed laser deposition and characterized using capacitive torque magnetometry and neutron measurements [1,2]. Our thin-film work has already shown that epitaxial strain and the amount of disorder in the spin ice films play important roles in determining their magnetic properties. In this talk, I will show how we have benchmarked capacitive torque magnetometry as a unique tool to characterize the transitions between noncollinear spin textures in spin-ice single crystals. Studying these magnetic-field-induced phase transitions allows extraction of Jeff and the MCP of monopole formation [3]. I will also talk about thin films grown on yttria-stabilized zirconia substrates, which we have investigated using the same approach. These films show modified spin ice physics depending on the growth conditions.

Beekman acknowledges the support of the National Research Foundation, under Grant No. NSF DMR-1847887 (CAREER). Use of National High Magnetic Field Laboratory user facilities was supported by NSF Cooperative Agreements No. DMR-1157490, No. DMR-1644779, and the state of Florida.

[1] K. Barry, B. Zhang, N. Anand, Y. Xin, A. Vailionis, J. Neu, C. Heikes, C. Cochran, H. Zhou, Y. Qiu, W. Ratcliff, T. Siegrist, & and C. Beekman, Phys. Rev. Materials, 3, 084412 (2019)

[2] C. Thompson, D. Reig-i-Plessis, L. Kish, A. A. Aczel, B. Zhang, E. Karapetrova, G. J. MacDougall, and C. Beekman, Phys. Rev. Materials 2, 104411 (2018)

[3] N. Anand, K. Barry, J. N. Neu, D. E. Graf, Q. Huang, H. Zhou, T. Siegrist, H. J. Changlani & C. Beekman, Nature Communications 13, 3818 (2022)