Abstract:We have investigated the kagomé ice behavior of the dipolar spin-ice compound Dy2Ti2O7 in a magnetic field along a [111] direction using neutron scattering and Monte Carlo simulations. The spin correlations show that the kagomé ice behavior predicted for the nearest-neighbor interacting model, where the field induces dimensional reduction and spins are frustrated in each two-dimensional kagomé lattice, occurs in the dipole interacting system. The spins freeze at low temperatures within the macroscopically dege… Show more
“…These kagome spins retain a fraction of the zero-field spin ice entropy, though still preserving the spin ice rules (two-in, two-out) of the parent pyrochlore system. This leads to classically disordered state, termed kagome ice 22,[24][25][26] , evidenced to date in several experimental studies on spin ice materials [27][28][29] .…”
Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z 2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.
“…These kagome spins retain a fraction of the zero-field spin ice entropy, though still preserving the spin ice rules (two-in, two-out) of the parent pyrochlore system. This leads to classically disordered state, termed kagome ice 22,[24][25][26] , evidenced to date in several experimental studies on spin ice materials [27][28][29] .…”
Actively sought since the turn of the century, two-dimensional quantum spin liquids (QSLs) are exotic phases of matter where magnetic moments remain disordered even at zero temperature. Despite ongoing searches, QSLs remain elusive, due to a lack of concrete knowledge of the microscopic mechanisms that inhibit magnetic order in materials. Here we study a model for a broad class of frustrated magnetic rare-earth pyrochlore materials called quantum spin ices. When subject to an external magnetic field along the [111] crystallographic direction, the resulting interactions contain a mix of geometric frustration and quantum fluctuations in decoupled two-dimensional kagome planes. Using quantum Monte Carlo simulations, we identify a set of interactions sufficient to promote a groundstate with no magnetic long-range order, and a gap to excitations, consistent with a Z 2 spin liquid phase. This suggests an experimental procedure to search for two-dimensional QSLs within a class of pyrochlore quantum spin ice materials.
“…Owing to the microscopic nature of these rare-earth spins, the energy scale of the interactions is below 1 K, which requires cryogenic conditions for any experimental investigation. The method of choice for measuring spin correlations in these systems is neutron scattering [1,[3][4][5][6]. An attractive alternative to the pyrochlore class of spin-ice systems is provided by 'artificial spin ice'-regular nanolithographic arrays of in-plane magnetized nanoscale magnets.…”
Artificial spin-ice systems consisting of nanolithographic arrays of isolated nanomagnets are model systems for the study of frustration-induced phenomena. We have recently demonstrated that monopoles and Dirac strings can be directly observed via synchrotronbased photoemission electron microscopy, where the magnetic state of individual nanoislands can be imaged in real space. These experimental results of Dirac string formation are in excellent agreement with Monte Carlo simulations of the hysteresis of an array of dipoles situated on a kagome lattice with randomized switching fields. This formation of one-dimensional avalanches in a two-dimensional system is in sharp contrast to disordered thin films, where avalanches associated with magnetization reversal are twodimensional. The self-organized restriction of avalanches to one dimension provides an example of dimensional reduction due to frustration. We give simple explanations for the origin of this dimensional reduction and discuss the disorder dependence of these avalanches. We conclude with the explicit demonstration of how these avalanches can be controlled via locally modified anisotropies. Such a controlled start and stop of avalanches will have potential applications in data storage and information processing.
“…22 Another way to distinguish between the theoretical models for the origin of the low temperature fluctuations is to explicitly test one of their predictions. Importantly, when the quantum spin ice model 9 is applied to Tb 2 Ti 2 O 7 it is predicted that for small fields applied along the [111] crystal axis a similar evolution between magnetic states to that in the thoroughly investigated partial magnetization plateaux [24][25][26][27] in Dy 2 Ti 2 O 7 and Ho 2 Ti 2 O 7 will be observed, albeit with a far smaller characteristic field scale, < ∼ 0.1 T. At the lowest temperatures, ≪ 0.1 K, a partial magnetization plateau should be evident 23 in this field region. While the underlying magnetic states should persist to slightly higher temperatures the small bandwidth of the energy levels results in the predicted plateau being smeared by around 0.1 K. The energy scales for Tb 2 Ti 2 O 7 are significantly reduced due to the effect of the quantum fluctuations.…”
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