New magnetic structure study of TbNi ₅ : Evidence of incommensurate structure

Abstract

RENi 5 (RE=rare-earth ions) intermetallic compounds crystallize in the hexagonal CaCu 5 structure (space group P6/mmm) [1] and have been extensively studied for various reasons over the last decades. Magneto-crystalline anisotropy of rare-earth ions as well as indirect exchange interaction between them, so-called RKKY interaction, is important to understanding the magnetism of these systems.We have investigated the magnetic structure of TbNi 5 using neutron diffraction from 2.2 to 30 K using neutron diffraction studies to understand new magnetic satellites below T C = 23 K, which have never been reported before. These satellites can be indexed as (0, 0, 1 ± τ ), (1, 0, 1 ± τ ), (0, 0, 2 ± τ ), and (1, 0, 2±τ ), where τ is equal to 0.0194 r.l.u. (reciprocal lattice units) by analyzing the diffraction patterns. We have observed these new peaks in addition to magnetic peaks seen in previous measurements. We can understand this longperiod incommensurate structure in terms of two propagation vectors: k 1 = (0, 0, 0) and k 2 = (0, 0, τ). Our neutron diffraction measurements clearly show that TbNi 5 has an incommensurate magnetic structure over the whole temperature range below the magnetic ordering of T C = 23 K. Our studies, together with bulk measurements, suggest that TbNi 5 should have a modulated magnetic structure over the whole temperature range from 23 to 2 K, in contradiction to the long held view that TbNi 5 is a collinear ferromagnet below T C = 23 K.[1] J.H. Wernick and S. Geller, Acta Cryst. 12 (1995) 662.[2] Seongsu Lee et al., EuroPhys. Lett. 63 (2003) 350.

Magnetic, magnetocaloric and neutron diffraction studies on TbNi5−xMx (M=Co and Fe) compounds

“…This indicates the onset of long range ferromagnetic ordering in the system. No superlattice reflections were observed, which rules out any antiferromagnetic ordering, unlike in the case of TbNi 5 [8]. The ferromagnetic nature below 100 K is in conformity with the magnetization measurements, which shows an increase in the magnetization with lowering the temperature below 100 K. The best solution for the magnetic structure was arrived by placing the magnetic moment on Tb ion only.…”

“…Among these compounds, TbNi 5 has received the attention of many researchers. There are a few reports on the magnetic and neutron diffraction studies in TbNi 5 and its derivatives [7][8][9][10][11][12]. The ordering temperature (T C ) of TbNi 5 is 24 K. However, below this temperature, it is not a collinear ferromagnet, but is reported to possess a modulated ferromagnetic structure [7,8].…”

“…Among these compounds, TbNi 5 has received the attention of many researchers. There are a few reports on the magnetic and neutron diffraction studies in TbNi 5 and its derivatives [7][8][9][10][11][12]. It is observed that in TbNi 5 , the moment is carried by Tb mostly and that the Ni sublattice (almost completely 3d shell) has negligible contribution to the moment.…”

Determining the magnetic ground state of TbNi5 single crystal using polarized neutron scattering technique

“…Using unpolarized neutron diffraction on poly-and single crystalline TbNi 5 samples we first found magnetic satellites besides the previously reported ferromagnetic contributions to Bragg reflections [16,17]. We then described the magnetic ordering in TbNi 5 as a fan-like incommensurate structure with the wave vector k ¼ 2p=cð0; 0,0:019Þ for temperatures between T P ¼ 23 K and T L ¼ 10 K. Below T L the TbNi 5 undergoes another magnetic phase transition from the incommensurate phase to a so-called ''lock-in'' phase.…”

Commensurate-incommensurate magnetic phase transition induced in TbNi5 by an external magnetic field

“…Our previous neutron diffraction studies of poly crystalline and single crystal TbNi 5 [15,16] showed that the Bragg reflections and magnetic satellites exist in all neutron diffraction patterns (NDPs) obtained at temperatures below T p . The NDPs can be described well on the assumption that in TbNi 5 there is formed a fanlike magnetic structure with two wave vectors k 1 = 0 and k 2 = 2πc/(0, 0, τ) with τ ≈ 0.18.…”