Magnetic-field-controlled spin valve and spin memory based on single-molecule magnets

A single-molecule magnet is a long-sought-after nanoscale component because it can enable us to miniaturize nonvolatile memory storage devices.The signature of a single-molecule magnet is switching between two bistable magnetic ground states under an external magnetic field.Based on this feature,we theoretically investigate a magnetic-fieldcontrolled reversible resistance change active at low temperatures in a molecular magnetic tunnel junction,which consists of a single-molecule magnet sandwiched between a ferromagnetic electrode and a normal metal electrode.Our numerical results demonstrate that the molecular magnetism orientation can be manipulated by magnetic fields to be parallel/antiparallel to the ferromagnetic electrode magnetization.Moreover,different magnetic configurations can be“read out”based on different resistance states or different spin polarization parameters in the current spectrum,even in the absence of a magnetic field.Such an external magnetic field-controlled resistance state switching effect is similar to that in traditional spin valve devices.The difference between the two systems is that one of the ferromagnetic layers in the original device has been replaced by a magnetic molecule.This proposed scheme provides the possibility of better control of the spin freedom of electrons in molecular electrical devices,with potential applications in future high-density nonvolatile memory devices.

Pure spin-current diode based on interacting quantum dot tunneling junction

A magnetic field-controlled spin-current diode is theoretically proposed,which consists of a junction with an interacting quantum dot sandwiched between a pair of nonmagnetic electrodes.By applying a spin bias VS across the junction,a pure spin current can be obtained in a certain gate voltage regime,regardless of whether the Coulomb repulsion energy exists.More interestingly,if we applied an external magnetic field on the quantum dot,we observed a clear asymmetry in the spectrum of spin current IS as a function of spin bias,while the charge current always decays to zero in the Coulomb blockade regime.Such asymmetry in the current profile suggests a spin diode-like behavior with respect to the spin bias,while the net charge through the device is almost zero.Different from the traditional charge current diode,this design can change the polarity direction and rectifying ability by adjusting the external magnetic field,which is very convenient.This device scheme can be compatible with current technologies and has potential applications in spintronics or quantum processing.

Mullite Oxidation Resistant Coating for SiC-coated Carbon/Carbon Composites by Supersonic Plasma Spraying

To improve the oxidation resistance of carbon/carbon （C/C） composites, mullite coating was prepared on the surface of SiC-coated C/C composites by supersonic plasma spraying. Phases and microstructures of mullite coating were characterized by X-ray diffraction （XRD） and scanning electron microscopy （SEM）. The coating primarily consists of a single phase of mullite （3AI203-2SIO2）. The SEM results show that mullite coating was continuous and well bonded with the SiC inner layer without penetrating crack. Mullite coating exhibited good oxidation resistance, After 98.5 h oxidation at 1773 K and 9 thermal shock cycles between 1773 K and room temperature, the weight loss of the coated C/C composites was only 2.57%.