Chemical potential induced phase transitions

Abstract

A simple electrical set-up to detect phase transitions is proposed and applied to a series of investigated samples: Gd, Cr, TiNi and CuZnSn, all exhibiting different types of phase transitions. The sample is glued to a contact electrode (here Ag) and immersed into a thermostat. We measure the electrical resistivity of the contact electrode as function of temperature. Due to the fact that the chemical potentials of the sample and the contact electrode should be equal (µ s = µ e ) the electron gas of the contact electrode "feels" a phase transition taking place in the investigated sample. Therefore we observe kinks in the resistivity plot of the contact electrode which easily localize the proper critical temperatures: T C (Gd), T N (Cr) and T struct (TiNi, CuZnSn). The proposed method visualizes the prevailing role of the chemical potential at phase transitions and provides a completely new ("remote") tool to detect critical points in solids. IntroductionThe chemical potential related to the electron gas of a system can be considered as a global quantity able to reflect all critical (or characteristic) points connected with different types of phase transitions (transformations) possible to appear in solids with varying temperature, pressure, concentration, etc. . Direct observation of the chemical potential critical behaviour has been performed by the use of electrochemical cells [21,22]. A quite new approach anticipated theoretically [25] is based on the temperature dependence of the resistivity of the contact electrode connected to a sample exhibiting phase transitions. Due to this method the critical temperatures of the sample should be observed as subtle but measurable kinks in the resisivity plot of the reference electrode. Astonishigly enough, the effect really exists. Here we report on some direct observations which allow to localize critical temperatures connected with different types of phase transitions taking place in Gd, Cr, TiNi and CuZnSn materials.

Chemical potential induced phase transition in the metallic electrode attached to the ferroelectric Pb5Ge3O11 single crystal

“…Till now, Refs. [15,17,18], the effect of the induced phase transition has been confirmed experimentally for metallic samples only i.e. for magnetic transitions in Gd, Cr, GdAl 2 and structural transitions in NiTi, CuZnSn when using various contact electrodes (Cu, Ag).…”

“…The results of the papers [15,17,18] indicate that the critical temperatures of the metallic samples can be detected in this way. However, this conclusion asks another question concerning the applicability of the method to a broader class of materials like non-metallic solids.…”

“…It is worthwhile to notice that the observed relative effect of the resistance deviation from the linear dependence is small, in accordance with Refs. [15,17,18].…”

Structural and optical properties of Zn0.9Mn0.1O/ZnO core-shell nanowires designed by pulsed laser deposition

“…17 However, also the FX A ͑n =2͒ and the FX B have been reported at the same energy. 19 A weak and broad line at about 3.323 eV is located in the energy range expected for the two-electron recombination as previously proposed by Reynolds et al 18 Figure 4͑b͒ shows the temperature dependent Besides the UV emission, deep level recombination is also observed in the measured PL spectra as can be seen in the inset of Fig. 4͑a͒, in the spectrum taken at 5.8 K. Figures 5͑a͒ and 5͑b͒ show high-resolution spectra of the structured green emission for the Zn 0.9 Mn 0.1 O / ZnO core-snowlike-shell samples grown on the a-Al 2 O 3 and GaN ͑buffer layer͒/Si ͑111͒ substrates, respectively.…”

Electrons and bursting waterworks

“…This effect is obviously extremely small, but changes in resistivity can be measured with a very high accuracy, so in principle this could work. In a paper which appears as Rapid Research Note (www.pss-rapid.com) in the present issue of physica status solidi (b), Matlak and collaborators claim to have observed just this effect at the magnetic phase transition of a number of different magnetic substances [8]. The observed changes of the resistivity are indeed quite small.…”