Spin tunneling properties in mesoscopic magnets: effects of a magnetic field

The tunneling of a giant spin at excited levels is studied theoretically in mesoscopic magnets with a magnetic field at an arbitrary angle in the easy plane. Different structures of the tunneling barriers can be generated by the magnetocrystalline anisotropy, the magnitude and the orientation of the field. By calculating the nonvacuum instanton solution explicitly, we obtain the tunnel splittings and the tunneling rates for different angle ranges of the external magnetic field ($\theta_{H}=\pi/2$ and $\pi/2<\theta_{H}<\pi$). The temperature dependences of the decay rates are clearly shown for each case. It is found that the tunneling rate and the crossover temperature depend on the orientation of the external magnetic field. This feature can be tested with the use of existing experimental techniques.Comment: 27 pages, 4 figures, accepted by Euro. Phys. J.

STUDY ON ADJUSTABLE CONNECTOR OF RECIPROCAL FRAME

In this paper, we design an adjustable connector of reciprocal frame, and a three-dimensional solid model of this connector with Circular Hollow Section has been created in the FEM software Abaqus CAE to study its mechanical properties. When the plastic hinge is formed at the end of the Circular Hollow Section, the connector is still in an elastic state. It is concluded that the adjustable connector of reciprocal frame has high strength and rigidity, realizing the goal for designing higher connector strength over Circular Hollow Section strength. Then parametric analysis is used to analyse the influence of the connector about each part on the mechanical properties, and the flexural rigidity of the connector has been derived. A three-dimensional wire model of reciprocal frames has been created in the FEM software Abaqus CAE, and a full-scale test model of the structure is designed. The numerical simulation results agree well with the test results. It is verified that the reliability of the modeling method and the accuracy of the connector mechanical model