15558

1574 دكتري

دكتري

ماده چگال تجربي

اصفهان : دانشگاه صنعتي اصفهان

1398

هفده، 171ص : مصور، جدول، نمودار

پرويز كاملي

اسماعيل عبدالحسيني سارسري

مجتبي اعلايي، محمد رضا محمدي زاده، محمود كدخدايي

1399/03/09

كتابنامه

فيزيك

فيزيك

1399/03/13

2607017

Experimetal and computational investigation of the effect of Zn and Cu doping on Ni Mn Sn and Ni Mn Ga ferromagnetic heusler alloys Ali Ghotbi Varzaneh ghotbi1130@gmail com January 21 2020 Department of Physics Isfahan University of Technology Isfahan 84156 83111 Iran University Code IUT 77142 Degree Ph D Language Farsi supervisor Dr Parviz Kameli kameli@iut ac ir Abstract In this project the Ni Mn Sn and Ni Mn Ga alloys have been prepared by Zn and Cu doping The obtained results on magnetic and structural properties of these alloys show that the martensitic transition MT increases and shifts to near room temperature due to the changes in number of conduction electrons per atom e a and the unit cell volume Then the magnetocaloric properties of these alloys have been calculated and measured by indirect and direct methods The obtained results by direct method show that the Zn doping of the Ni Mn Sn alloy led to a significant enhancement of the value of the adiabatic temperature changes Tad Further study on cyclic behavior of magnetocaloric effect indicates the response of these alloys decreases under subsequent magnetic field and this is the challenging part for practical application in refrigeration To induce a reversible transition due to the wide temperature hysteresis a combination of a magnetic field with a significant external mechanical effect is needed Ab initio computations were carried out to provide the theoretical guide to gain a deeper insight into the role of Zn and Cu dopant in the MT and magnetism By ab intitio calculation the site occupancy variation of Zn was analyzed The results demonstrated that in a fully ordered structure Zn atoms prefer to occupy the sublattice of the host element in deficiency The effective parameter on MT temperature was explained using the density of state and tetragonality results The second part of the project was focused on the structural and magnetic properties of Ni Mn Ga alloys The obtained results show that the martensite phase of these samples contains modulated structure and therefore they have the potential for using in magnetic shape memory actuator Our magnetic characterization indicates the kinetic arrest phenomenon in Ni Mn Ga alloy and due to this effect the good magnetocaloric effect can not be expected

پرويز كاملي

اسماعيل عبدالحسيني سارسري

مجتبي اعلايي، محمد رضا محمدي زاده، محمود كدخدايي