Abstract
The pyrochlore compounds Ho2Ti2O7 and Dy2Ti2O7 show an exotic form of magnetism called the spin ice state, resulting from the interplay between geometrical frustration and ferromagnetic coupling. A fascinating feature of this state is the appearance of magnetic monopoles as emergent excitations above the degenerate ground state. Over the past years, strong effort has been devoted to the investigation of these monopoles and other properties of the spin ice state in bulk crystals. Here, we report the fabrication of Ho2Ti2O7 thin films using pulsed laser deposition on yttria-stabilized ZrO2 substrates. We investigated the structural properties of these films by X-ray diffraction, scanning transmission electron microscopy, and atomic force microscopy, and the magnetic properties by vibrating sample magnetometry at 2 K. The films not only show a high crystalline quality, but also exhibit the hallmarks of a spin ice: a pronounced magnetic anisotropy and an intermediate plateau in the magnetization along the [111] crystal direction.
Highlights
The magnetic Ho3+ ions in Ho2Ti2O7 form a lattice of corner-sharing tetrahedra in the pyrochlore structure and interact via ferromagnetic coupling.1–7 Their magnetic moments are Ising-like due to the crystal field anisotropy and are aligned along the set of 111 axes
The possibility of making thin films will further advance the research into spin ice systems and the manipulation of the monopole states, and this study presents a crucial step towards the generation of real devices for “magnetronics.”
The lattice mismatch of yttria-stabilized zirconia (YSZ) with Ho2Ti2O7 is 2% (Fig. 1(a)) and, prior to deposition, the YSZ substrates are annealed at 1050 ◦C to obtain a smooth surface
Summary
The magnetic Ho3+ ions in Ho2Ti2O7 form a lattice of corner-sharing tetrahedra in the pyrochlore structure and interact via ferromagnetic coupling.1–7 Their magnetic moments are Ising-like due to the crystal field anisotropy and are aligned along the set of 111 axes. The studies on the crystal structure confirm the high quality of the Ho2Ti2O7 films, the most important question is whether these films show the spin ice behavior.
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