Study Of Phase Transition And Magnetization Characteristics On Nanowire

Nanomaterials have many special physical properties, in contrast to those in the bulkmaterial. So they can be used in information storage, sensors and medical applications,especially the magnetic nanomaterial. Therefore, the phase transition and magnetizationcharacteristics of nanowire are playing significant roles in the future technologicaldevelopment, and these studies have been turn into a research hotspot in recent years.In this paper, we have investigated the phase transition and magnetizationcharacteristics of the single layer and double layers core/shell nanowires with theco-existence of crystal field and transverse field in the frame of Ising model. We writeprograms in the use of matlab software, and take advantage of numerical calculation tostudy the effects of exchange interaction, crystal field and transverse field onmagnetization, initial susceptibility, internal energy, specific heat, transition temperature,compensation temperature and hysteresis loops. The results indicate that the nanowiresystems have multi-compensation points and multi-circles of hysteresis loop and theseproperties can have potential used in the magnetic storage materials.In the certain physical parameters, the total magnetization of single core/shellnanowire has shown the curves of Q、P、N which have been predicted in the theory of Néel. The exchange interaction, crystal field and transverse field have tremendous effects onthe shapes of total magnetization and the value of saturation magnetization. We alsoobtained the new type of total magnetization curves when the total magnetization is thatdrawing the summation and average of core and shell respectively and then calculating anaverage of the obtained calculations. The new type of curve has two compensation pointsin the certain physical parameters which didn′t predict in the theory of Néel. The initialsusceptibility appears singularity phenomenon at the transition temperature Tc. Thetransition temperature Tcis decreasing with the increase ofDb JabandΩ Jab,however it has critical value in the TcversusΩ Jab. And then the transitiontemperature Tcincrease with the increase ofJ bJab. The changes of the transitiontemperature Tcin the phase diagram are agreement with the changes of the transition temperature Tcin the curves of magnetization. The compensation temperature Tcomponlyexists in certain parameters. Internal energy is rapidly increased as the temperature risesuntil it reaches a phase transition at the point of inflection point and increased slowly afterthe phase transition point. The curves of specific heat have peaks before the transitiontemperature Tcand then the specific heat has a sharp decline at the phase transition point.All in all, the shapes of specific heat like a saddle. With the changes ofΩ Jab,J aJab,Db JabandJ bJab, the shape of the hysteresis loop changes from zero circle to sevencircles, and the areas of the hysteresis loop are also changed.To the double core/shell nanowire, the total magnetization has two compensationpoints in certain parameters. The effects of exchange interaction, crystal field andtransverse field on saturation magnetization are similar as those in the single core/shellnanowire. The different layers of the core have dramatically influence on themagnetization, transition temperature and compensation temperature of nanowire. Thetransition temperature versusDb JabandJ bJabare the same as single core/shellnanowire. With the increase ofΩ bJab, the transition temperature decreases at smallvalue ofΩ bJaband then declines to a stable level without critical value. There are twocompensation points at certain parameters in the double layers of core/shell nanowire. Theinternal energy versus temperature and specific heat versus temperature in the doublelayers of core/shell nanowire are similar to the single core/shell nanowire. In contrast to thehysteresis loop of single core/shell nanowire, the maximum circles of the hysteresis loopare five in the double layers of core/shell nanowire.