Field Induced Unusual Magnetic Behavior at Low Temperature in Pr0.67Ca0.33MnO3Pr_{0.67}Ca_{0.33}MnO_3

In this study, magnetic properties of $Pr_{0.67}Ca_{0.33}MnO_3$ compound were investigated in detail. The magnetization versus temperature (M-T) curve showed that this material undergoes a charge order transition at 200 K. A more pronounced FM phase appeared below 56 K. At T = 5 K, a field induced sharp step like magnetisation transition associated with phase separation was observed. However, after application of 7 T magnetic field at 5 K, the magnetic behaviour of sample was changed completely and full FM behaviour was observed. The more interesting is that the sample remains in the FM state and does not retrieve the initial magnetic state until warmed up to charge order transition temperature. Large negative magnetic entropy change (- 26.18 J/(kg K) at 38 K and 5 T) was attributed to step like magnetisation transition

Production of LaCaMnO3LaCaMnO_3 Composite by Ball Milling

$La_{0.67}Ca_{0.33}MnO_3$ perovskite-type manganite was synthesized by high-energy ball milling raw oxides of $La_2O_3$ (purity 99.9%), $CaCO_3$ (purity > 99%), and MnO (purity > 99%). The ratio of ball and powder weight was 10:1 and the rotating speed was set to 500 rpm. X-ray analysis indicated that $La_{0.67}Ca_{0.33}MnO_3$ single phase was formed completely when milling time is up to 4 h. The peak intensity of perovskite structure decreased and a hump-like peak appeared with further milling time. When the milling time is longer than 40 h, the perovskite structure disappeared and the amorphous phase was formed completely. Scanning electron microscopy picture of 24 h milled sample showed that the particle size generally varies in a broad range from nanometer scale to a few μm. The magnetic measurements showed that ball milling samples have an inhomogeneous magnetic state and exhibit spin-glass like behavior. The significantly small magnetic entropy change and a remarkably broad temperature interval in entropy change were attributed to high degree of structural and magnetic disorder and broadening of magnetic transition

The German Corporate Governance Code: general acceptance and neuralgic norms – a second look

Based on a survey of all the companies listed at the Frankfurt Stock Exchange, this paper analyses the extent of compliance with the German Corporate Governance Code. The investigation includes the recommendations as well as the suggestions of the Code. Overall, findings indicate a high level of Code conformity. Furthermore, the Code continues to contribute to the changes of the governance modalities of German firms. Nonetheless, Code standards remain which gain comparably less acceptance. We identify those norms, which are still rejected by the majority of the surveyed corporations and discuss why these compliance rates are currently low and whether they can be expected to increase in the future.compliance; corporate governance; German Corporate Governance Code; statement of conformity; public policy; Germany.

Compliance with the German Corporate Governance Code: an empirical analysis of the compliance statements by German listed companies

In 2002, the German Corporate Governance Code was adopted. This paper examines the overall acceptance of the Code recommendations and identifies its critical standards that receive comparably less agreement among German listed companies. The study is based on the compliance declarations of 408 firms listed at the Frankfurt Stock Exchange. The findings indicate a significantly high level of Code conformity which can be expected to increase in the future. Comparative analyses reveal that company size is positively associated with the extent of Code compliance. Neuralgic norms concern the personal liability and compensation of the board members, the staffing of the boards, the structure of the supervisory board and accounting requirements. Copyright Blackwell Publishing Ltd 2005.

Crack Detection Using Fluxgate Magnetic Field Sensor

In this study, the variation of the magnetic flux distribution in a magnetised ferromagnetic material which has in homogeneity as a crack is studied. An orthogonal fluxgate magnetic field sensor was used in the inspection of cracks. In the fluxgate sensor, the sensing element $(Co_{0.94}Fe_{0.06})_{72.5}Si_{12.5}B_{15}$ amorphous ferromagnetic wire was placed inside a pickup coil winding with 50 μm copper wire and connected to a signal generator and the output from pick-up coil was detected using a lock-in amplifier. The surface profile of magnetic materials with a crack was obtained using a specially designed 3-dimensional moving system. A large decrease in the output voltage of the sensor was observed when the sensor was moved on the top of the crack, after the further movement of the sensor the output voltage came back to the previous value

Crystallisation Kinetics of Co_{75-x}M_xSi_{15}B_{10} (M = Fe, Mn, Cr and x=0, 5) Amorphous Alloys

In this study, the effect of Fe, Mn and Cr substitution for Co on the crystallization kinetics of amorphous $Co_{75-x}M_xSi_{15}B_{10}$ (M = Fe, Mn and Cr; x=0 and 5) alloys were investigated. The broad diffraction peaks in the X-ray diffraction patterns for as-quenched ribbons indicated that all of the samples exhibit an amorphous structure. The activation energies of the alloys were calculated from differential thermal analysis data using the Kissinger, Ozawa and Augis-Bennett models. The increased activation energy for Fe, Mn and Cr doped samples indicated that the thermal stability and the crystallization kinetics were improved in the doped samples. The value of the Avrami exponent indicated that the crystallization is typical diffusion controlled three-dimensional growth for all of the samples

YIG Film for Magnetic Field Sensor

Single crystal $Y_3Fe_5O_{12}$ (YIG) film was grown onto (111) oriented gadolinium gallium garnet (GGG) substrate by the liquid phase epitaxy (PLD) technique. The X-ray diffraction measurements showed that epitaxial growth of the film along its (111) axis. The surface characteristic was investigated by atomic force microscopy (AFM) measurement. The magnetic field sensor consisted of a rectangular shape with 5 mm wide, 15 mm long and 5 μm thick YIG film and a pair of identical 50 μm wide microstrip copper transducers elements separated by 6 mm. The filter was tested by measuring reflection $S_{11}$ characteristic at various bias magnetic fields. The results have showed that when the bias field increased from 0 to 2.5 kOe, the frequency value corresponding to $S_{11}$ maxima increased from 1 GHz to 9 GHz. This suggests that the wide range magnetic field sensing and the highly sensitive field sensing are simultaneously fulfilled with the YIG film