Magnetic structure of theS=1Ni5(TeO3

Abstract

Magnetization, neutron diffraction, and antiferromagnetic resonance measurements were employed to investigate the magnetic ground state of Ni 5 ͑TeO 3 ͒ 4 Br 2 single crystal. Despite the layered topology of the Ni 2+ sites, typical for frustrated antiferromagnets, the system orders antiferromagnetically below T N = 29 K. Noncollinear arrangements of the Ni sublattices having a very complex temperature dependence were found from the neutron diffraction and magnetization measurements. Single-ion anisotropy, associated with the strongly distorted Ni-centered octahedra, has the same magnitude as the antiferromagnetic exchange interaction. The effect of these anisotropies prevails over the geometrical frustration leading to a long-range magnetic ordering below T N .

Magnetic phase diagram of the two-dimensional antiferromagnetNi5(TeO3)4Br<

“…This allowed us to determine a magnetic phase diagram of this compound in the temperature range between 300 and 1.7 K and in magnetic fields from 0 up to 23 T. Below T N , several different AFM phases were identified and successfully explained with a molecular-field approach, developed in our previous AFMR report. 6 We stress that the observed richness of the phase diagram is a direct consequence of the competition between intracluster and intercluster exchange couplings on the one hand and single-ion magnetic anisotropy on the other hand.…”

“…6 The dominant magnetic interactions between the Ni 2+ are indeed antiferromagnetic, as indicated by high-temperature susceptibility data, implying a negative Curie temperature Ϸ −50 K. The system exhibits a long-range Néel ordered state below T N =29 K. [4][5][6][7][8] Consequently, the empirical frustration parameter, ͉͉ / T N = 1.7, is rather small. Neutron magnetic diffraction and unusual temperature dependence of the antiferromagnetic resonance ͑AFMR͒ frequency, 6,9 however, suggest a very complicated temperature dependence of the Ni 2+ sublattice magnetizations in the ordered phase. This reflects the importance of competition between various magnetic terms, possibly leading to intriguing magnetic structures as a function of temperature and external magnetic field.…”

Multiferroic FeTe2O5Br: Alternating spin chains with frustrated interchain interactions

“…Magnetic anisotropies can be determined by ESR, [29][30][31][32] which in the magnetically ordered state allows a detection of collective low-energy magnetic excitations at Q = 0, ± q ICM -the so-called antiferromagnetic resonance (AFMR) modes.…”

High-field magnetization of a two-dimensional spin frustration system, Ni5(TeO3)4X2(X = Br, Cl)

“…According to the results of neutron and X-ray diffraction measurements, there are 20 Ni 2+ ions in an unit cell (Z-factor = 4). The Ni ions locate in three different crystallographic sites, in which Ni1 is in Wyckoff site 4e; Ni2 and Ni3 are in Wyckoff site 8f [3,6]. The spin orientations depend on the Ni sites.…”

“…The anisotropic properties were investigated on single crystal Ni 5 (TeO 3 ) 4 Br 2 , showing the g =2.45 and g ⊥ =2.53 [5]. Recently, the noncollinear arrangements of the Ni sublattices of Ni 5 (TeO 3 ) 4 Br 2 were observed by neutron diffraction and magnetization measurements [6]. These studies reveal very complicated spin interactions and a unique ground state.…”