Intrinsic double-peak structure of the specific heat in low-dimensional quantum ferrimagnets

Motivated by recent magnetic measurements on A3Cu3(PO4)4 (A=Ca,Sr) and Cu(3-Clpy)2(N3)2 (3-Clpy=3-Chloropyridine), both of which behave like one-dimensional ferrimagnets, we extensively investigate the ferrimagnetic specific heat with particular emphasis on its double-peak structure. Developing a modified spin-wave theory, we reveal that ferromagnetic and antiferromagnetic dual features of ferrimagnets may potentially induce an extra low-temperature peak as well as a Schottky-type peak at mid temperatures in the specific heat.Comment: 5 pages, 6 figures embedded, Phys. Rev. B 65, 214418 (2002

SKILL EVALUATION OF MOVEMENT BASED ON HUMAN LIMB ELECTRICAL IMPEDANCE

The purpose of this work is to propose a skill evaluation of tennis movement based on forearm electrical impedance and its measurement method. We try to evaluate the pattern of movement using the pattern of impedance waveform and the stability of movement using the reproducibility of impedance waveform. It can be intuitively evaluated reproducibility and mobility of serve movement using waveform of forearm electrical impedance (Z). Consequently 4 parameters which show reproducibility and mobility using waveform of Z was defined. We made a trial about principal component analysis of Z during serve and got a scatter diagram of first second principal component about 9 subjects including skilful and beginner players. Then the principal component analysis devided subjects into skilful and beginner players. The measurement method of Z used the four electrodes technique based on constant current(50 k Hz,500 uA). Z changes with the changes of cross sectional area of muscle and blood volume caused by the change of joint angle and acceleration. Hence Z has information of movement. The results of this experiment was as follows. In waveforms of Z during serve with a ball and without a ball, each waveform of a skillful player was very similar to each other, but each waveform of a beginner player was not. Z of a skillful player varied more than that Z of a beginner player, because the movement of a skillful player is larger than that of a beginner player. The advantages of this method are as follows. There is no spatial and temporal limitation for measurement. The subject is scarcely restricted in movement. Although we must select appropriate locations of electrodes in each type of movement, this method can be expected to have applications for various sports

Evidence for Carrier-Induced High-Tc Ferromagnetism in Mn-doped GaN film

A GaN film doped with 8.2 % Mn was grown by the molecular-beam-epitaxy technique. Magnetization measurements show that this highly Mn-doped GaN film exhibits ferromagnetism above room temperature. It is also revealed that the high-temperature ferromagnetic state is significantly suppressed below 10 K, accompanied by an increase of the electrical resistivity with decreasing temperature. This observation clearly demonstrates a close relation between the ferromagnetism with extremely high-Tc and the carrier transport in the Mn-doped GaN film.Comment: 9 pages, 3 figure