arXiv subjects

Zachary T. LaDuca

Publications and source records attributed to Zachary T. LaDuca.

3 recordsLinked to original sources

arXiv2026

Remote epitaxial frustration stabilizes a correlated interfacial state

Remote epitaxy exploits substrate interactions transmitted across atomically thin materials to replicate substrate crystal structure. Here we show that competition among graphene-, substrate-, and reconstruction-derived interactions can instead produce frustration. Using GdAuGe films on $N$-layer graphene/SiC(0001), we identify at intermediate $N$ a self-limited interfacial state with broken long-range translational order, accompanied by non-monotonic crystallographic orientation selection in the epitaxial film above. The frustrated interface is accompanied by strongly enhanced magnetic irreversibility above 300 K, with an interface-dominated rather than volume-scaled response, linking epitaxial frustration to an emergent collective property. Annealing drives an initially epitaxial crystal into the frustrated state, distinguishing it from kinetically trapped disorder. First-principles calculations reveal a multi-periodic interfacial potential that provides a microscopic basis for frustration. Together, these results establish epitaxial frustration as a materials-design principle for stabilizing correlated interfacial states and emergent collective properties.

cond-mat.mtrl-sci↗

arXiv2026

Strain patterning of flexomagnetism

Flexomagnetism, the coupling of magnetic ordering to strain gradients, provides access to novel symmetry-broken magnetic phases that cannot be accessed via uniform strain. However, flexomagnetism is hard to understand because it is extremely difficult to control a spatially varying strain. Here, we develop a top-down strategy to pattern transverse strain gradients using helium ion implantation through a lithographically defined mask. Using epitaxial films of the antiferromagnetic nodal line semimetal GdAuGe, we demonstrate that transverse strain gradients $\partial \varepsilon_{zz}/\partial x$ induce near-room-temperature ferromagnetic response, compared to the retained para or antiferromagnetism for homogeneously strained GdAuGe. We spatially correlate the magnetic response with the regions of largest strain gradient, via magnetic force microscopy and nanobeam x-ray diffraction, respectively, to confirm the flexomagnetic response. Our approach opens new avenues for the precise control of magnetic phases in thin films of quantum materials via a patterned strain gradient.

cond-mat.mtrl-sci↗

arXiv2022

Controlling the balance between remote, pinhole, and van der Waals epitaxy of Heusler films on graphene/sapphire

Remote epitaxy on monolayer graphene is promising for synthesis of highly lattice mismatched materials, exfoliation of free-standing membranes, and re-use of expensive substrates. However, clear experimental evidence of a remote mechanism remains elusive. In many cases, due to contaminants at the transferred graphene/substrate interface, alternative mechanisms such as pinhole-seeded lateral epitaxy or van der Waals epitaxy can explain the resulting exfoliatable single-crystalline films. Here, we find that growth of the Heusler compound GdPtSb on clean graphene on sapphire substrates produces a 30 degree rotated epitaxial superstructure that cannot be explained by pinhole or van der Waals epitaxy. With decreasing growth temperature the volume fraction of this 30 degree domain increases compared to the direct epitaxial 0 degree domain, which we attribute to slower surface diffusion at low temperature that favors remote epitaxy, compared to faster surface diffusion at high temperature that favors pinhole epitaxy. We further show that careful graphene/substrate annealing ($T\sim 700 ^\circ C$) and consideration of the film/substrate vs film/graphene lattice mismatch are required to obtain epitaxy to the underlying substrate for a variety of other Heusler films, including LaPtSb and GdAuGe. The 30 degree rotated superstructure provides a possible experimental fingerprint of remote epitaxy since it is inconsistent with the leading alternative mechanisms.

cond-mat.mtrl-sci↗