8410

7790

كارشناسي ارشد

فيزيك

اصفهان: دانشگاه صنعتي اصفهان، دانشكده فيزيك

1392

[ده]،96ص.: مصور،جدول،نمودار

ص.ع.به فارسي و انگليسي

مجتبي اعلايي

جواد هاشمي فر

28/10/92

فرهاد شهبازي، اسماعيل عبدالحسيني

فيزيك

ID7790

به فارسي و انگليسي: قابل رويت در نسخه ديجيتالي

9AbstractThe geometrical frustration in the magnetic pyrochlore oxides A2B2O7 causesinteresting properties at the low temperatures in these materials Er2Ti2O7 is a themagnetic pyrochlore oxides with space group Fd 3 m Er local magnetic momentsconfined to planes orthogonal to the local 111 axes so we can describe the system in amodel so called XY like model we consider the system by using an ab intio method Density Functional Theory DFT with Fleur code in LDA LDA U LDA U SOCapproximation To take into account the f electrons coulomb interactions correctly weemployed LDA U a Hubbard method correction We gained energy gap equal to 2 99 eVfrom analysis of the density of states The spin orbit coupling SOC is very effective inthese materials so we added SOC to the LDA U calculations LDA U SOC UsingLDA U SOC we consider the effect of non collinear magnetism The LDA U SOCcalculations in the all in spin configuration give rise to the magnetic moments 8 2 B forEr2Ti2O7 This value deviates from the experimental results The reason is that the DFTcalculations are trapped in the local minima so we need more sophisticated methods tofind the global minimum in our electronic structure calculations The analysis of thedensity of states of Erbium titanium and oxygen in the crystal show that Er 4f statehybridizes with O 2p weakly and so the 4f orbitals remain well localized Keywords Magnetic pyrochlore oxides geometrical frustration Exchange Interaction Collinear magnetism Non collinear magnetism Density Functional Theory

مجتبي اعلايي

جواد هاشمي فر

فرهاد شهبازي، اسماعيل عبدالحسيني