Geometrical Frustration and Planar Triangular Antiferromagnetism in Quasi-Three-Dimensional Artificial Spin Architecture

Abstract

We present a realization of highly frustrated planar triangular antiferromagnetism achieved in a quasi-three-dimensional artificial spin system consisting of monodomain Ising-type nanomagnets lithographically arranged onto a deep-etched silicon substrate. We demonstrate how the three-dimensional spin architecture results in the first direct observation of long-range ordered planar triangular antiferromagnetism, in addition to a highly disordered phase with short-range correlations, once competing interactions are perfectly tuned. Our work demonstrates how escaping two-dimensional restrictions can lead to new types of magnetically frustrated metamaterials.

Low-energy states, ground states, and variable frustrations of the finite-size dipolar Cairo lattices

“…1(b)], and 600 nm allows direct control and manipulation of competing dipolar interactions [63]. In accordance with previous work [63,[66][67][68], the thickness and overall dimensions of the nanoislands were chosen to result in a blocking temperature (temperature at which thermally induced moment reorientations occur at a time scale 042129-7 of a few seconds) around 130 K. Each nanoisland is small enough, to be in the monodomain state, and elongated, so that magnetic moments can only point in one of two possible directions along the long axis of a given nanoisland. Thus, each nanoisland represents a single Ising macrospin.…”

“…9(b)]. It is obvious that the experimental system attempts to access a long-range ordered ground state, but as shown in previous studies on various artificial frustrated spin systems, fabrication-related intrinsic disorder, and the blocking temperature of the nanomagnets can significantly slow down and hinder relaxation towards a long-range ordered ground state [64,65,68]. The free energy minimum must correspond to stable thermodynamic equilibrium and the realization of the most probable state.…”

Artificial out-of-plane Ising antiferromagnet on the kagome lattice with very small farther-neighbor couplings

“…We see two possible sources of such couplings: the simple dipolar interaction between the regions with OOP anisotropy, and a possible interaction (of dipolar nature or some more subtle origin) between the regions with IP anisotropy. Here, we determine the likelihood of these scenarios by performing micromagnetic simulations [53][54][55][56][57].…”

Geometrical frustration and competing orders in the dipolar trimerized triangular lattice

“…The real-space observations are quantitatively evaluated by extracting nearest-neighbor correlation measures, as has been done for other artificial spin ice systems [2,3,5,21]. A correlation measure C between moments such as α and β [see Fig.…”

“…The structure with b = 545 nm had a blocking temperature T B = 142 K, and we conducted our temperature-dependent observations up to a temperature of 205 K. At six different temperatures between 142 K and 205 K, we recorded XMCD image sequences containing 70-100 images at each temperature. Magnetic configurations recorded within these image sequences allows us to extract temperature-dependent magnetic structure factors [13,19,21] [see Figs. 5(a .…”