Abstract Non‐collinear antiferromagnets (AFMs) are an exciting new platform for studying intrinsic spin Hall effects (SHEs), phenomena that arise from the materials’ band structure, Berry phase curvature, and linear response to an external electric field. In contrast to conventional SHE materials, symmetry analysis of non‐collinear antiferromagnets does not forbid non‐zero longitudinal and out‐of‐plane spin currents with polarization and predicts an anisotropy with current orientation to the magnetic lattice. Here, multi‐component out‐of‐plane spin Hall conductivities are reported in L12‐ordered antiferromagnetic PtMn3thin films that are uniquely generated in the non‐collinear state. The maximum spin torque efficiencies (ξ =JS /Je ≈ 0.3) are significantly larger than in Pt (ξ ≈ 0.1). Additionally, the spin Hall conductivities in the non‐collinear state exhibit the predicted orientation‐dependent anisotropy, opening the possibility for new devices with selectable spin polarization. This work demonstrates symmetry control through the magnetic lattice as a pathway to tailored functionality in magnetoelectronic systems.
more »
« less
Investigation of the monopole magneto-chemical potential in spin ices using capacitive torque magnetometry
Abstract The single-ion anisotropy and magnetic interactions in spin-ice systems give rise to unusual non-collinear spin textures, such as Pauling states and magnetic monopoles. The effective spin correlation strength (Jeff) determines the relative energies of the different spin-ice states. With this work, we display the capability of capacitive torque magnetometry in characterizing the magneto-chemical potential associated with monopole formation. We build a magnetic phase diagram of Ho2Ti2O7, and show that the magneto-chemical potential depends on the spin sublattice (αorβ), i.e., the Pauling state, involved in the transition. Monte Carlo simulations using the dipolar-spin-ice Hamiltonian support our findings of a sublattice-dependent magneto-chemical potential, but the model underestimates theJefffor theβ-sublattice. Additional simulations, including next-nearest neighbor interactions (J2), show that long-range exchange terms in the Hamiltonian are needed to describe the measurements. This demonstrates that torque magnetometry provides a sensitive test forJeffand the spin-spin interactions that contribute to it.
more »
« less
- PAR ID:
- 10368283
- Publisher / Repository:
- Nature Publishing Group
- Date Published:
- Journal Name:
- Nature Communications
- Volume:
- 13
- Issue:
- 1
- ISSN:
- 2041-1723
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract 19F magnetic resonance (MR) based detection coupled with well‐designed inorganic systems shows promise in biological investigations. Two proof‐of‐concept inorganic probes that exploit a novel mechanism for19F MR sensing based on converting from low‐spin (S=0) to high‐spin (S=1) Ni2+are reported. Activation of diamagneticNiL1andNiL2by light or β‐galactosidase, respectively, converts them into paramagneticNiL0, which displays a single19F NMR peak shifted by >35 ppm with accelerated relaxation rates. This spin‐state switch is effective for sensing light or enzyme expression in live cells using19F MR spectroscopy and imaging that differentiate signals based on chemical shift and relaxation times. This general inorganic scaffold has potential for developing agents that can sense analytes ranging from ions to enzymes, opening up diverse possibilities for19F MR based biosensing.more » « less
-
Abstract Polarons and spin-orbit (SO) coupling are distinct quantum effects that play a critical role in charge transport and spin-orbitronics. Polarons originate from strong electron-phonon interaction and are ubiquitous in polarizable materials featuring electron localization, in particular 3d transition metal oxides (TMOs). On the other hand, the relativistic coupling between the spin and orbital angular momentum is notable in lattices with heavy atoms and develops in 5d TMOs, where electrons are spatially delocalized. Here we combine ab initio calculations and magnetic measurements to show that these two seemingly mutually exclusive interactions are entangled in the electron-doped SO-coupled Mott insulator Ba2Na1−xCaxOsO6(0 < x < 1), unveiling the formation ofspin-orbital bipolarons. Polaron charge trapping, favoured by the Jahn-Teller lattice activity, converts the Os 5d1spin-orbital Jeff = 3/2 levels, characteristic of the parent compound Ba2NaOsO6(BNOO), into a bipolaron 5d2Jeff = 2 manifold, leading to the coexistence of different J-effective states in a single-phase material. The gradual increase of bipolarons with increasing doping creates robust in-gap states that prevents the transition to a metal phase even at ultrahigh doping, thus preserving the Mott gap across the entire doping range from d1BNOO to d2Ba2CaOsO6(BCOO).more » « less
-
Abstract The crystal structure, electron energy-loss spectroscopy (EELS), heat capacity, and anisotropic magnetic and resistivity measurements are reported for Sn flux grown single crystals of orthorhombic Pr2Co3Ge5(U2Co3Si5-type,Ibam). Our findings show thato-Pr2Co3Ge5hosts nearly trivalent Pr ions, as evidenced by EELS and fits to temperature dependent magnetic susceptibility measurements. Complex magnetic ordering with a partially spin-polarized state emerges nearTsp= 32 K, with a spin reconfiguration transition nearTM= 15 K. Heat capacity measurements show that the phase transitions appear as broad peaks in the vicinity ofTspandTM. The magnetic entropy further reveals that crystal electric field splitting lifts the Hund’s rule degeneracy at low temperatures. Taken together, these measurements show that Pr2Co3Ge5is an environment for complexfstate magnetism with potential strongly correlated electron states.more » « less
-
Abstract Spin waves, collective dynamic magnetic excitations, offer crucial insights into magnetic material properties. Rare‐earth iron garnets offer an ideal spin‐wave (SW) platform with long propagation length, short wavelength, gigahertz frequency, and applicability to magnon spintronic platforms. Of particular interest, thulium iron garnet (TmIG) has attracted huge interest recently due to its successful growth down to a few nanometers, observed topological Hall effect, and spin‐orbit torque‐induced switching effects. However, there is no direct spatial measurement of its SW properties. This work uses diamond nitrogen‐vacancy (NV) magnetometry in combination with SW electrical transmission spectroscopy to study SW transport properties in TmIG thin films. NV magnetometry allows probing spin waves at the sub‐micrometer scale, seen by the amplification of the local microwave magnetic field due to the coupling of NV spin qubits with the stray magnetic field produced by the microwave‐excited spin waves. By monitoring the NV spin resonances, the SW properties in TmIG thin films are measured as a function of the applied magnetic field, including their amplitude, decay length (≈50 µm), and wavelength (0.8–2 µm). These results pave the way for studying spin qubit‐magnon interactions in rare‐earth magnetic insulators, relevant to quantum magnonics applications.more » « less