Metamagnetism and crystal-field splitting in pseudohexagonal CeRh3Si2
Physical Review B American Physical Society 105:12 (2022) 125119
Abstract:
CeRh 3 Si 2 has been reported to exhibit metamagnetic transitions below 5 K, a giant crystal field splitting, and anisotropic magnetic properties from single crystal magnetization and heat capacity measurements. Here we report results of neutron and x-ray scattering studies of the magnetic structure and crystal-field excitations to further understand the magnetism of this compound. Inelastic neutron scattering and resonant inelastic x-ray scattering reveal a J z = 1 / 2 ground state for Ce when considering the crystallographic a direction as quantization axis, thus explaining the anisotropy of the static susceptibility. Furthermore, we find a total splitting of 78 meV for the J = 5 / 2 multiplet. The neutron diffraction study in zero field reveals that, on cooling from the paramagnetic state, the system first orders at T N 1 = 4.7 K in a longitudinal spin density wave with ordered Ce moments along the b axis (i.e., the [0 1 0] crystal direction) and an incommensurate propagation vector k = ( 0 , 0.43 , 0 ). Below the lower-temperature transition T N 2 = 4.48 K , the propagation vector locks to the commensurate value k = ( 0 , 0.5 , 0 ) , with a so-called lock-in transition. Our neutron diffraction study in applied magnetic field H ∥ b axis shows a change in the commensurate propagation vector and development of a ferromagnetic component at H = 3 kOe , followed by a series of transitions before the fully field-induced ferromagnetic phase is reached at H = 7 kOe . This explains the nature of the steps previously reported in field-dependent magnetization measurements. A very similar behavior is also observed for the H ∥ [0 1 1] crystal direction.Inhomogeneous spin excitations in weakly coupled spin-1/2 chains
Physical Review Research American Physical Society 4:1 (2022) 013111
Abstract:
We present a systematic inelastic neutron scattering and neutron diffraction study on the magnetic structure of the quasi-one-dimensional spin- 1 2 magnet SrCo 2 V 2 O 8 , where the interchain coupling in the Néel-type antiferromagnetic ground state breaks the static spin lattice into two independent domains. At zero magnetic field, we have observed two new spin excitations with small spectral weights inside the gapped region defined by the spinon bound states. In an external magnetic field along the chain axis, the Néel order gets partially destabilized at μ 0 H ★ = 2.0 T and completely suppressed at μ 0 H p = 3.9 T , above which a quantum disordered Tomonaga–Luttinger liquid (TLL) prevails. The low-energy spin excitations between μ 0 H ★ and μ 0 H p are not homogeneous, containing the dispersionless (or weakly dispersive) spinon bound states excited in the Néel phase and the highly dispersive psinon-antipsinon mode characteristic of a TLL. We propose that the two new modes at zero field are spinon excitations inside the domain walls. Since they have a smaller gap than those excited in the Néel domains, the underlying spin chains enter the TLL state via a local quantum phase transition at μ 0 H ★ , making the Néel/TLL coexistence a stable configuration until the excitation gap in the Néel domains closes at μ 0 H p .Magnetic monopole density and antiferromagnetic domain control in spin-ice iridates
Nature Communications Springer Nature 13:1 (2022) 444
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.Real Space Imaging of Spin Stripe Domain Fluctuations in a Complex Oxide
Physical Review Letters American Physical Society (APS) 127:27 (2021) 275301
Magnetic structure of the topological semimetal YbMnSb2
Physical Review B American Physical Society 104:16 (2021) L161103