Powder synthesis and crystal growth of Y2V2O7 under high pressure and its physical properties

Crystal-field, exchange interactions and magnetism in pyrochlore ferromagnet R2V2O7 (R3+=Y, Lu)

“…The temperature dependence of the dc magnetic susceptibility w dc of polycrystalline sample of Y 2 V 2 O 7 was measured by Haghighirad et al [6] in the temperature range of 2-300 K. w obeys CurieWeiss (CW) behavior down to 150 K with paramagnetic Curie temperature y CW ¼86(71) K indicating the dominance of ferromagnetic (FM) exchange interactions between V 4 þ -moments and effective paramagnetic moment m eff ¼1.76m B /V which is close to the spin-only free-ion value of 1.734m B for 3d 1 ions. The susceptibility deviates from the CW behavior below T m ¼ 150 K and is observed to increase sharply below 100 K with FM ordering temperature at T C $ 68 K. It is found in the present work that such thermal variation of w dc , particularly above T C , is due to the coordinated effect of CF interactions in presence of appreciable SOC, and exchange and dipolar interactions among magnetic V-spins.…”

“…The observed [6][7][8] A 1g À 2 E g 0 splitting of the 2 T 2g state becomes $ 3216 cm À 1 and total splitting of the 2 D term now becomes 16,210 cm À 1 . These splittings are also found to be smaller than those of Y 2 V 2 O 7 due to the fact that trigonal distortion (compression) of the VO 6 octahedra is smaller in Lu 2 V 2 O 7 , since the deformation of the octahedra is determined by the 48f oxygen positional parameter x [2] which is 0.4129(9) and 0.4202(6) for Lu 2 V 2 O 7 and Y 2 V 2 O 7 [6], respectively.…”

“…Furthermore these vanadate pyrochlores are unique and intriguing, because they are 3d ferromagnets with magnetic ordering temperature T C E 68 K [6] and 70 K [6][7][8], and at the same time Mott insulators having band gap D bg ¼0.33 eV [9], contrary to the common belief that ferromagnetism leads usually to metallic character [1]. In these materials, electronic configuration of V 4 þ (3d 1 , S ¼1/2) ions is (t 2g ) 1 (e g ) 0 and the orbital ordering pattern determined by the neutron diffraction [10] showed that each orbital is extended along the four local /111S directions towards the center-of-mass of the elementary V 4 -tetrahedron.…”

“…Therefore in the present study, our aim is to simulate the reported thermal dependence of dc susceptibility w [6,7], saturated magnetization, paramagnetic Curie temperature y CW , and magnetic specific heat [8] of Y 2 V 2 O 7 and Lu 2 V 2 O 7 by considering atomic-like electronic structure associated with V 4 þ ions under the D 3d CF by properly taking account of spin-orbit coupling and also considering inter-site spin-spin interactions term (molecular field). We present our calculations for CF parameters (CFP) which define cubic (octahedral) CF and its trigonal distortion at V-site, directional magnetic moments and local magnetic susceptibilities, anisotropic g-values and exchange tensors in these vanadate pyrochlores, and we also analyze and compare their effects on the magnetic and electronic properties vis-a-vis structural properties of these compounds in understanding these properties collectively.…”

Single-ion anisotropy, Dzyaloshinskii-Moriya interaction, and negative magnetoresistance of the spin-12pyrochloreR2VXiang1, Kan2, Whangbo3 et al. 2011Phys. Rev. B424260View full textAdd to dashboardCite

“…In the following, we report results obtained with U = 3 eV and J = 1 eV on V, but the dependence of our results on U and J will be also discussed. It was found 16 to some convergence difficulties so that our calculations focused mainly on Y 2 V 2 O 7 using its experimental structure 16 . The structural optimization was found to have a negligible effect on its magnetic properties.…”