Search

We exploit the recoil loop measurements to study the asymmetric magnetization reversal in an exchange-biased La0.37Sr0.33MnO3/La0.33Ca0.67MnO3 bilayer film. It is found that the recoil curve encloses a marked area only in the second quadrant of the hysteresis loop, and the recoil susceptibility in the descending branch of the major loop is evidently higher than that in the ascending branch. The study indicates that the exchange anisotropy of a unidirectional nature and an orientation deviated from the easy axis of the ferromagnetic layer plays a crucial role in creating the reversal asymmetry.

We have found phase separation in La0.45Sr0.55MnO3-δ (LSMO) by means of electron spin resonance, magnetic force microscopy (MFM) and magnetic measurements. Ferromagnetic and antiferromagnetic phases can coexist at low temperatures and ferromagnetic and paramagnetic phases coexist when the temperature lies between the Neel and Curie temperatures. The size and shape of the ferromagnetic phases (the minority phases) was first observed directly from MFM images. It is suggested that the phase separation in LSMO is not the charge segregation type, but an electroneutral type due perhaps to the nonuniform distribution of oxygen vacancies.

Magnetic and transport properties of La0.5Ca0.5MnO3 have been investigated by measuring the magnetization and resistance in zero-field-cooled (ZFC) and held-cooled (FG) modes. Conspicuously irreversible behaviors of magnetization/resistance in the two different modes were observed below the charge ordering transition temperature (T-CO) The ZFG and FC magnetizations at 5K, as functions of the magnetic field, coincide for mu(0)H less than or equal to 1T Afterwards, the ZFC magnetization tends to an approximate constant, but the FC one increases linearly with increasing field. There exists an excellent correspondence between magnetization and resistance below T-CO All the results suggest that the ferromagnetic clusters embed in the charge-ordered matrix. The phenomenon of ferromagnetic clusters growing up easily in the FC procedure has been interpreted according to the model of thermally activated two-level system.

A new tabletop confocal micro x-ray fluorescence setup with an MCBM 50-0.6B x-ray tube is assembled. The confocal micro x-ray fluorescence setup includes two lenses, a polycapillary full lens in the excitation channel and a polycapillary half lens in the detection channel. A Ni-Cr wire in diameter 25 μm is used to investigate the FWHM of three-dimensional confocal volume. A basso-relievo capital letter of a 1-jiao RMB coin of 2005 version is studied with this confocal micro x-ray fluorescence setup.

Structural, magnetic, and transport properties of perovskite La2/3Ca1/3Mn1-xSixO3 (x = 0, 0.025, 0.05) have been studied. The incorporation of Si decreases the overall resistivity, but obviously increases the Curie temperature (TC), metal-insulator transition temperature (TP), and the magnetoresistance ratio MR (defined as [R(0) - R(H)]/R(0)) near room temperature. Comparing with La2/3Ca1/3MnO3, the TC, TP, and MR of the sample with x = 0.05 increase by 30, 45K, and 20%, respectively. Lattice effects may play a more important role than the magnetic dilution in the case of low Si substitution.

The polycrystalline perovskite-phase PT/PZT/PT ferroelectric thin film was prepared by sol-gel method. The domain and domain wall structures were investigated by scanning force microscopy. The out-of-plane polarization(OPP), in-plane polarization(IPP), the OPP amplitude and OPP phase images were obtained. The domain of the film has a complex structure with c-domain and deviated-c-domain the direction of which deviated from the surface normal of the film. The complex domain structure is related to the orientation of the crystal grains in the film. For the［111］oriented films, the 180° domain wall is formed when deviated-c-domains have reverse directions in OPP and IPP. The 90° domain wall is formed when the domains have the same direction in OPP and reverse directions in IPP, or when they have reverse directions in OPP and same direction in IPP.

Lanthanum doped lead titanate (PLT) ferroelectric thin films were grown on Pt/Ti/SiO2/Si(100) substrates using RF magnetron sputtering. X-ray Diffraction (XRD) was applied to study crystalline properties of PLT films, and XRD patterns of PLT thin films show that there appeared (111) preferred-oriented tetragonal perovskite phase. The ferroelectric domain patterns and the corresponding topography of PLT thin films have been investigated using piezoresponse force microscopy (PFM) and atomic force microscopy (AFM), respectively. PFM observations show that there exist nanoscale banded 90° domain patterns 20 to 60 nm in width and low energy head-to-tail polarization configurations in PLT film. The relationship between fabricating conditions and properties of PLT10 thin films was studied. It was found that PLT10 thin film fabricated under the optimized conditions possess dielectric constant εr=365, dielectric loss tgδ=0.02, and pyroelectric coefficient γ=2.18×10-8C·(cm2·K)-1, respectively. The PLT thin films could meet the needs for uncooled pyroelectric infrared sensors.

The cantilever split-morph, a new type of piezoelectric actuator, have been designed for dual-stage head positioning servo system of high density hard disk drives. In this actuator configuration, a PZT ceramic plate, with one end mechanically clamped and the other free, was poled along its thickness and divided into two symmetric parts along length by splitting electrodes. Driving voltages are preferably so arranged that they make one of the two parts expand by the “31”action while the other part, i.e., the symmetric part, contracts. This will result in a bending motion of the actuator along the direction of its width. The driving voltage-tip displacement characteristics of the actuator have been investigated by theoretical analysis, finite element modeling and experiment. Theoretical analysis indicated that the electric field induced stress is much smaller than stretch strength of piezoelectric ceramic. Tip displacement measured by Michelson interferometer is a little larger than the calculated result. This is mainly due to the increase of piezoelectric coefficient d31 at high driving field. Tip displacement of 1 to 2μm can be achieved at 20 to 50V driving voltage for the split-morph whose size is similar to that of the existing suspension. As to 25 kTPI (track per inch) high track density hard disk drives, this actuating stroke can cover at least one track width and meet the primary requirements of dual-stage head positioning servo system for displacement of the secondary actuator.

We have prepared antiferroelectric ceramics with compositions of (Pb0.97La0.02)(Zr1-x-ySnyTix)O3(x=0.09 or 0.1; 0.16≤y≤0.38) near antiferroelectric (AFE)tetragonal-ferroelectric (FE)rhombohedral morphotropic phase boundary. The effects of Sn content on electric field-induced AFE→FE switching field Ec, double-hysteresis-loop width ΔE, and temperature-induced FE→AFE phase transition temperature TFE, AFE→paraelectric (PE) transition temperature Tc are investigated. At constant Ti content x, both TEF and Tc decrease with increase of Sn content y. Electric hysteresis loop measurement demonstrates an increase of Ec and decrease of ΔE when Sn content y increases. Furthermore, we also find that Ec and ΔE are related with TFE and Tc. In situ X-ray diffraction under dc bias field shows that symmetry changes from tetragonal phase to rhombohedral phase with an increase of c axis,and an increase of lattice volume.