科研之友
微信
新浪微博
Facebook
分享链接
摘要
The magnetic structures of the two bismuth oxy-phosphate compounds BiMPO(5) (M(2+) = Ni(2+), Co(2+)) have been determined by neutron powder diffraction using group theory analysis as a preliminary tool. Both compounds adopt a monoclinic crystal structure (S. G. P2(1)/n, a = 7.1642(2) angstrom, b = 11.2038(3) angstrom, c = 5.1740(2) angstrom and beta = 107.296(2). for Ni(2+) and a = 7.2441(1) angstrom, b = 11.2828(1) angstrom, c = 5.2258(1) angstrom and beta = 107.841(1). for Co(2+)). The refinement of the magnetic structures below T(N) = 17.5 and 15 K, respectively, for both compounds show that the magnetic structure is characterized by the propagation vector k = (-1/2, 0, 1/2), with components given with respect to the reciprocal lattice of the nuclear structure. This means a magnetic unit cell that is a multiple of the nuclear cell. The magnetic structure is constituted of ferromagnetic pairs of metal ions antiferromagnetically coupled within double chains. The relative strength of the intra and inter double chains exchange interactions has been examined by establishing a theoretical magnetic phase diagram. Most of the interactions come from M-O-O-M super-super-exchange paths. At its ground state, BiNiPO(5) shows a nearly collinear arrangement of magnetic moments with m(1.5) (K) = 2.13(3) mu(B)/ Ni. Due to the strong magnetic anisotropy of Co(2+) (m(1.5) (K) = 3.52(3) mu B/Co), the collinear character is largely lost while the magnetic structure remains analysable on the basis of the greatest isotropic component of the local moments.
- 出版日期2008-10-15
- 单位中国地震局
