Temperature and magnetism

Ac-susceptibility measurements on (Ga,Mn)As with x = 0.042 have been performed in alternating B from 0.1-4 mT. In the temperature dependence of susceptibility, there is a sharp peak at about 48 K at 0.1 mT, which suggests a ferromagnetic phase transition. The temperature and magnetic field dependence is rather complicated and an increase of B involves additional peaks (the number of which up to 4), which may be due to domain formation and domain wall movement (Sadowski et al. 2000). There is also a report about ac-susceptibility measurements on (Ga,Mn)As with x = 0.07, which shows that there is no difference between the field-cooled and zero-field cooled ac-susceptibilities measured with B = 10 mT (Van Esch et al. 1997). 

Analysis of Hall-effect data has been one of the most widely used techniques for studying conduction mechanisms in solids, especially semiconductors. For the single-carrier case, one readily obtains carrier concentrations and mobilities, and it is usually of interest to study these as functions of temperature. This can supply information on the predominant charge-carrier scattering mechanisms and on activation energies, i.e., the energies necessary to excite carriers from impurity levels into the conduction band. Where two or more carriers are present, the analysis becomes more complex, but much more information can be obtained from sludies of the temperature and magnetic held dependencies. 

Gliemann et al. also studied the luminescence of systems with vibrational structure [31], viz. the Se4+ ion in Cs2SeCl6 and Rb2SeCl6. Figure 10 presents the emission spectrum of Cs2SeOe as a function of temperature and magnetic field. The low-temperature emission intensity increases with temperature as well... 

Fig, 10. Emission spectra of Cs2SeCl6 as a function of temperature and magnetic field strength. Reproduced with permission from Ref. [31]... 

Figs. 3 and 4 display the series of temperature and magnetic field dependencies of the dV/dl curves with their BTK fittings, respectively. Here at low field (temperature), the two separate sets of the gap minima... 

Additional insights into molecular motion can also be obtained by studying solvent effects on relaxation times and their temperature and magnetic field dependencies as demonstrated on siloxanes by Kosfeld and coworkers67. 

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