Complex bound states of magnetic excitations, known as Bethe strings, were predicted almost a century ago to exist in one-dimensional quantum magnets1. The dispersions of the string states have so ...far remained the subject of intense theoretical studies2–7. Here, by performing neutron scattering experiments on the one-dimensional Heisenberg–Ising antiferromagnet SrCo2V2O8 in high longitudinal magnetic fields, we reveal in detail the dispersion relations of the string states over the full Brillouin zone, as well as their magnetic field dependencies. Furthermore, the characteristic energy, the scattering intensity and linewidth of the observed string states exhibit excellent agreement with our precise Bethe–ansatz calculations. Our results establish the important role of string states in the quantum spin dynamics of one-dimensional systems, and will invoke studies of their dynamical properties in more general many-body systems.In one-dimensional quantum magnets, complex bound states of magnetic excitations known as Bethe strings have long been predicted. Now, a detailed neutron scattering study of SrCo2V2O8 reveals their magnetic-field-dependent dispersion relation.
Precision thermal Hall measurements unlock potential for unraveling fundamental thermal transport principles in novel materials. This work addresses the challenge of resolving sub-mK temperature ...differences in magnetic fields by employing high-precision capacitance thermometry with thermalized electronics, achieving a background noise of approximately Image 1 at Image 2. The novelty lies in the improvement and combination of innovative approaches, including the application of attenuators for thermal anchoring, a modular multi-stage approach to reduce thermal gradients, direct thermometer-sample assembly, and the use of individual capacitance bridges for faster measurements. The setup performance is demonstrated for the pyrochlore oxide terbium titanate and the longitudinal and transverse thermal conductivities agree with the literature. We show that the transverse temperature difference is proportional to the product of magnetic field times heating power for fields up to Image 3, enabling improved statistics compared to individual sweeps analysis. We conduct an analysis of uncertainties in the transverse thermal conductivity, considering various thermometer calibrations for extracting temperature differences. This analysis reveals a significant influence of the longitudinal conductivity on the transverse thermal conductivity. These advancements allow for unprecedented temperature resolution and stability, while identified resolution limitations pave the way for next-generation setups.
The random fluctuations of spins give rise to many interesting physical phenomena, such as the 'order-from-disorder' arising in frustrated magnets and unconventional Cooper pairing in magnetic ...superconductors. Here we show that the exchange of spin waves between extended topological defects, such as domain walls, can result in novel magnetic states. We report the discovery of an unusual incommensurate phase in the orthoferrite TbFeO(3) using neutron diffraction under an applied magnetic field. The magnetic modulation has a very long period of 340 Å at 3 K and exhibits an anomalously large number of higher-order harmonics. These domain walls are formed by Ising-like Tb spins. They interact by exchanging magnons propagating through the Fe magnetic sublattice. The resulting force between the domain walls has a rather long range that determines the period of the incommensurate state and is analogous to the pion-mediated Yukawa interaction between protons and neutrons in nuclei.
In most magnetic materials, the exchange interaction causes the spins on the neighboring sites of a crystal lattice to align. In the absence of exchange interactions, dipolar interactions, which are ...highly orientation dependent, are also expected to be able to cause magnetism. Kraemer et al. (p. 1416) present evidence for antiferromagnetism in a dipolar-coupled material, LiErF4. Although a three-dimensional system, its critical behavior was more reminiscent of a two-dimensional material. Magnetism has been predicted to occur in systems in which dipolar interactions dominate exchange. We present neutron scattering, specific heat, and magnetic susceptibility data for LiErF4, establishing it as a model dipolar-coupled antiferromagnet with planar spin-anisotropy and a quantum phase transition in applied field Hc|| = 4.0 ± 0.1 kilo-oersteds. We discovered non-mean-field critical scaling for the classical phase transition at the antiferromagnetic transition temperature that is consistent with the two-dimensional XY/h4 universality class; in accord with this, the quantum phase transition at Hc exhibits three-dimensional classical behavior. The effective dimensional reduction may be a consequence of the intrinsic frustrated nature of the dipolar interaction, which strengthens the role of fluctuations. PUBLICATION ABSTRACT
Gold nanotriangles with magnetite satellites Henning, Ricky; Liebig, Ferenc; Prietzel, Claudia ...
Colloids and surfaces. A, Physicochemical and engineering aspects,
09/2020, Letnik:
600
Journal Article
Recenzirano
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This work describes the synthesis of hybrid particles of gold nanotriangles (AuNTs) with magnetite nanoparticles (MNPs) by using 1-mercaptopropyl-3-trimethoxysilan (MPTMS) and ...L-cysteine as linker molecules. Due to the combination of superparamagnetic properties of MNPs with optical properties of the AuNTs, nanoplatelet-satellite hybrid nanostructures with combined features become available. By using MPTMS with silan groups as linker molecule a magnetic “cloud” with embedded AuNTs can be separated. In presence of L-cysteine as linker molecule at pH > pHiso a more unordered aggregate structure of MNPs is obtained due to the dimerization of the L-cysteine. At pH < pHiso water soluble positively charged AuNTs with satellite MNPs can be synthesized. The time-dependent loading with MNP satellites under release of the extinction and magnetization offer a hybrid material, which is of special relevance for biomedical applications and plasmonic catalysis.
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Pickering emulsions with two types of nanoparticles, i.e., superparamagnetic magnetite nanoparticles dispersed in n-hexane and gold nanoparticles dispersed in water, were formed by ...rigorous mixing in presence of surface active polymeric surfactants. Monodisperse magnetite nanoparticles with a mean particle size of 4 nm were obtained by a microwave-assisted synthesis in n-hexane in presence of oleic acid, and gold nanoparticles were produced in aqueous solution in presence of the hyperbranched poly(ethyleneimine) (PEI) or sodium citrate as reducing and stabilizing agent. After mixing the prepared nanoparticle dispersions in presence of the Pluronics an intermediate gel-like phase is formed. The Pickering emulsion droplets in the intermediate phase are stabilized by both types of nanoparticles, as to be seen by cryo-SEM micrographs. After separating, solvent evaporation and redispersion in water highly ordered Pluronic-stabilized superparamagnetic magnetite nanoparticle aggregates with embedded gold nanoparticles can be obtained.
The combination of magnetic nanoparticles and thermoresponsive nanogels represents an appealing strategy for the development of theranostic probes. These hybrid nanocarriers present several ...advantages such as outstanding properties for guided therapy, magnetic resonance imaging, and triggered release of encapsulated cargoes. Most magnetic thermoresponsive nanogels are built with strategies that comprise a physical interaction of particles with the polymeric network or the covalent attachment of a single particle to the linear polymer. Herein, we report a facile synthetic approach for the synthesis of magnetic and thermoresponsive nanogels that allows the controlled incorporation of multiple superparamagnetic inorganic cores as covalent cross-linkers. An ultrasonication-assisted precipitation-polymerization afforded nanogels with sizes in the nanometric range and similar magnetization and light transduction properties compared to the discrete magnetic nanoparticles. The theranostic capability of these nanocarriers was further investigated both
in vitro
and
in vivo
.
In vivo
experiments demonstrated the capacity of these materials as nanocarriers for near-infrared (NIR) triggered chemotherapy and highlighted the relevance of the correct concentration/dose in this antitumoral modality to achieve a superior therapeutic efficacy.
The combination of magnetic nanoparticles and thermoresponsive polymers to build multifunctional nanogels represents an appealing strategy for the development of theranostic probes.
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