Spectral observation of symmetry-protected selection rules for dynamical high-dimensional parity in alignment magnetic resonance

Multidimensional Floquet-driven alignment systems with dynamical symmetry present various exotic phenomena and applications.However,there are challenges in directly characterizing large-spin dynamical symmetry from spectra.Here,we first observe the symmetry-protected selection rules of dynamical high-dimensional parity in a large-spin(F=4)system.We theoretically construct a Floquet-driven alignment system that can be used to reveal high-dimensional spatiotemporal symmetry.In the experiment,the system is implemented in Cs atomic gas subjected to two-dimensional Floquet-modulated magnetic resonance driving.By developing Floquet detection protocols of alignment double-sided spectra,we directly verify symmetry-protected selection rules of dynamical high-dimensional parity for large-spin systems.This work advances the exploration of dynamical symmetry to large spins,and unravels a universal Floquet scheme for the investigation of symmetry-protected selection rules.

Influence of misch metal content on microstructure and magnetic properties of R–Fe–B magnets sintered by dual alloy method

MM14Fe79.9B6.1/Nd13.5Fe80.5B6 magnets were fabricated by dual alloy method（MM, misch metal）. Some magnets have two Curie temperatures. Curie temperatures Tc1corresponds to the main phase which contains more La Ce, and Tc1 decreases from 276.5℃ to 256.6℃ with the content of MM increasing from 30.3 at.% to 50.6 at.%. The variation of Br with the increase of MM indicates the existence of inter-grain exchange coupling in the magnets. When MM/R ≤ 30.3 at.%,the magnetic properties can reach the level of the intrinsic coercivity Hcj≥ 7.11 kOe and the maximum energy product（BH）max≥ 41 MGOe. Compared with Nd, La and Ce are easier to diffuse to the grain boundaries in the sintering process,and this will cause the decrease of H（cj） Due to the diffusion between the grains, the atomic ratio of La, Ce, Pr, and Nd in each grain is different and the percentage of Nd in all grains is higher than that in misch metal.

How light affect the magnetotactic behavior and reproduction of ellipsoidal multicellular magnetoglobules?

Magnetotactic bacteria(MTB)synthesize intracellular magnetic organelles,magnetosomes,which consist of magnetic crystals that are enveloped in a membrane.Magnetosomes are organized into a chain(s)and confer on cells a magnetic dipolar moment.This magnetic property allows MTB cells to align and swim along geomagnetic field lines,a movement referred to as magnetotaxis.Some MTB species change their swim direction in response to illumination by UV,violet and blue light.Here we analyzed the polarity of morphology,magnetism,and motion in Mediterranean multicellular magnetotactic prokaryotes,also called,magnetoglobules or MMP.The magnetoglobules were assembled from 60-80 cells into an asymmetric ellipsoidal morphology with a relative narrow and large end.They swam dominantly northward,parallel to the direction of the magnetic field,with the narrow-end as the leading side.In response to a reversal in the direction of the magnetic field,they aligned quickly along the magnetic field lines and kept swimming northward.Interestingly,under constant illumination,385-nm UV light,magnetoglobules changed their swimming direction southward anti-parallel to the direction of the magnetic field,with the large-end as the leading side.The change from a northward to southward direction occurred along with an increase of swimming speed.A minimum of 35-mW/cm^(2) irradiance of UV light was sufficient to trigger the swimming re-orientation.UV radiation also triggered the unidirectional division of magnetoglobules.Together these results revealed a coordination of the polarity of magnetoglobule morphology,magnetic moment,and swimming orientation,in response to magnetic and optical stimuli.The UV triggered the reversal of magnetotaxis and magnetoglobule division indicating the ecological significance of light for multicellular magnetotactic prokaryotes.

Fabrication of Bulk β-FeSi_2 Crystal With ThreeDimensional Alignment by an Oscillating Magnetic Field

It has been reported that an anisotropic magnetic field could produce the three-dimensional alignment of fine single-crystal particles with the orthorhombic crystal structure.However,the three-dimensional alignment was achieved only in suspensions.Fabrication of bulk 'single' materials that have the three-dimensional alignment of grains has been desired.This study proposes a procedure for the fabrication,which consists of slip casting under an oscillating magnetic field and sintering.Optimization of casting and sintering conditions achieved the three-dimensionally aligned bulk β-FeSi_2.

Perpendicularly Self-Oriented and Shape-Controlled L10-FePt Nanorods Directly Synthesized by a Temperature-Modulated Process

The synthesis and self-assembly of tetragonal phase-containing L10-Fe55Pt45 nanorods with high coercive field is described. The experimental procedure resulted in a tetragonal/cubic phase ratio close to 1：1 for the as-synthesized nanoparticles. Using different surfactant/solvent proportions in the process allowed control of particle morphology from nanospheres to nanowires. Monodisperse nanorods with lengths of 60 ＋ 5 nm and diameters of 2-3 nm were self-assembled in a perpendicular oriented array onto a substrate surface using hexadecylamine as organic spacer. Magnetic alignment and properties assigned, respectively, to the shape anisotropy and the tetragonal phase suggest that the self-assembled materials are a strong candidate to solve the problem of random magnetic alignment observed in FePt nanospheres leading to applications in ultrahigh magnetic recording （UHMR） systems capable of achieving a performance of the order of terabits/in2.

A Synthesis of Geophysical Data in Southeastern North China Craton:Implications for the Formation of the Arcuate Xuhuai Thrust Belt

The Xuhuai fold thrust belt(XHTB)is a curved structure in the southeastern margin of the North China Craton(NCC)that has attracted great attentions due to its tectonic and petrological characteristics.However,few geophysical studies have focused on the deep structure of this belt.In this study,we carry out a systematic demonstration of the main geophysical features that characterize the XHTB and surrounding areas.The results reveal small negative gravity and magnetic anomalies,thin crust and lithosphere,lower shear velocity and shallower earthquake epicenters relative to other areas of the NCC,collectively indicating a lithospheric-scale rheological anomaly at this belt.The magnetic alignments show a trend similar to that of geological units in southeastern NCC and adjacent areas,although they differ from the SKS-splitting fast polarization directions,except in the Qinling-Dabie orogen where a vertical coherent deformation of the crust and mantle may be involved there.Based on the geophysical data,we propose a detachment-controlled model,which was caused by the different detachment depth/strength,for the formation of XHTB to explain its arcuate shape as well as the magnetic alignments,thus providing new insight into the deep processes of southeastern NCC.

Method to Identify the Material of a Single Grain Based on Its Magnetization and Anisotropy Measured in a Chamber Type μG Drop Shaft

Free translation caused by attractive field-gradient force was observed for Ni and ferrite(CuFe_2O_4) grains that were released in a diffuse area.In order to exclude the effect of terrestrial gravity,translation was observed in micro-gravity(μG) condition produced by a compact drop-shaft installed in a ordinary laboratory room.Magnetization Ms per unit mass of the grain is obtained by analyzing the above-mentioned translations in terms of a energy conservation rule;here conservation of the sum of field-induced potential mMsH and kinetic energy 1/2/mv^2 is considered for a particle with mass m.The present method of obtaining Ms is free of measuring the mass of sample;this is because the field-gradient force is a volume force that is proportional to m.The method is also free of an interfering signal emitted from the sample holder.Accordingly,Ms is detectable irrespective of sample size,provided that the field-induced translation is observable.The above-mentioned procedure to estimate Ms from filed-induced translation is a step to obtain a reliable magnetic data from a single nano-sized grain.The efficiency of material identification was recently confirmed on various solid grains,which was based on diamagnetic magnetization data obtained from its translations caused by field-gradient repulsive force.A diamagnetic material generally possesses an intrinsic value of magnetic susceptibility and its anisotropy.The present results on nickel grains indicate that the principle of material identification based on its magnetization data is applicable for the three major category of magnetic materials,namely ferro-(or ferri-) magnetic, paramagnetic and diamagnetic material.