Magnetic monopole density and antiferromagnetic domain control in spin-ice iridates

Abstract

Magnetically frustrated systems provide fertile ground for complex behaviour, including unconventional ground states with emergent symmetries, topological properties, and exotic excitations. A canonical example is the emergence of magnetic-charge-carrying quasiparticles in spin-ice compounds. Despite extensive work, a reliable experimental indicator of the density of these magnetic monopoles is yet to be found. Using measurements on single crystals of Ho2Ir2O7 combined with dipolar Monte Carlo simulations, we show that the isothermal magnetoresistance is highly sensitive to the monopole density. Moreover, we uncover an unexpected and strong coupling between the monopoles on the holmium sublattice and the antiferromagnetically ordered iridium ions. These results pave the way towards a quantitative experimental measure of monopole density and demonstrate the ability to control antiferromagnetic domain walls using a uniform external magnetic field, a key goal in the design of next-generation spintronic devices.

Berry curvature induced spontaneous and topological-like Hall effect in magnetic Weyl semimetallic Nd2Ir2O7 (111) thin films

“…A recent single crystal study, along with Monte Carlo simulations for Ho 2 Ir 2 O7, shows that the A and B domain ratios will be ∼70:30. 34 However, in the present case, it may vary as Ho 3+ and Nd 3+ have different J eff values. MR data for the temperature range of 3-20 K have been plotted in Fig.…”

“…The appearance of dip and the presence of hysteresis in MR can be explained by the field-induced plastic domain deformation of Ir 4+ 5d moments from AOAI (B-domain) to AIAO (A-domain) for the applied positive field and from AIAO (A-domain) to AOAI (B-domain) for the negative field (H), respectively, along the [111] direction. 12,34 The domain imbalance of Ir 4+ occurs due to the field-induced modification of the Nd 3+ spin structure from 4-in-0-out (4I0O) to 1-in-3-out (1I3O) and 4-out-0-in (4O0I) to 1-in-3-out (1I3O), which creates an effective magnetic field (h loc ) at the Ir 4+ sites through f -d exchange interaction. At H = 0, both the A and B domains will be present in equal proportion in the sample.…”

“…For the cases of Ho 2 Ir 2 O7 and Nd 2 Ir 2 O7 single crystal studies, the application of field along the [001] direction stabilizes the Ho 3+ and Nd 3+ moments in a 2-in-2-out configuration, as confirmed by their magnetization measurements along the [001] direction. 12,34 The modified 2-in-2-out spin configuration of Nd 3+ 4 f moments may induce a 2-in-2-out state in Ir 4+ 5d moments via the f -d exchange interaction. Since both the A and B domains of Ir 4+ 5d moments with a 4-in-0-out spin structure will convert to 2-in-2-out ordering, no field-induced plastic domain deformation ARTICLE pubs.aip.org/aip/apm will occur for this particular [001] applied field direction.…”

Anomalous magnetoresistance by breaking ice rule in Bi2Ir2O7/Dy2Ti2O7 heterostructure

“…For instance, the correlated d-electrons in pyrochlore iridates not only exhibit an all-in-all-out ordering of their own at much higher temperatures, but also force the same magnetic order onto the A-site sublattice regardless of the rare earth element 21 . In some cases, the interactions within the rare earth sublattice may modify the transport properties of the d-electron [22][23][24] at lower temperatures, such as the fragmented monopole crystal ground state 25 as well as the monopoledensity-related magneto-transportation 26 . However, the spin state of the rare earth sublattice is often impaired by the energy scale of the delectrons, which is much larger than the interaction.…”

Fragmented Spin Ice and Multi- k Ordering in Rare-Earth Antiperovskites

“…This constraint results in extensive ground-state degeneracy [2,[4][5][6], long-range dipolar correlations [7][8][9], and fractionalized excitations that behave as emergent magnetic monopoles [10][11][12][13][14][15], a phenomenology known as the Coulomb phase [16,17]. Spin ice, and derivatives such as quantum spin ice [10,18,19] and monopole-crystalline fragmented spin ice [20][21][22], are among the best-studied frustrated magnets due to the abundance of rare-earth pyrochlore materials with large local moments [23].…”