Weak ferromagnetism in ${\text{TbNi}}_{2}{\text{B}}_{2}\text{C}$

Weak ferromagnetism in ${TbNi}_{2} B_{2} C$

H. Kawano-Furukawa, H. Tsukagoshi, T. Nagata, C. Kobayashi, H. Yoshizawa, and H. Takeya

Phys. Rev. B 77, 144426 – Published 24 April 2008

Abstract

The nature of the magnetic structure and its ordering process into the weak ferromagnetic (WFM) phase of ${TbNi}_{2} {{}^{11}B}_{2} C$ has been carefully investigated by an unpolarized neutron diffraction technique. The results show that at low temperature, there appear several spin density wave peaks that can be indexed by two independent propagation vectors, $q_{1}^{'}$ and $q_{2}$ . Detailed measurements at various temperatures further reveal that magnetic peaks indexed by $q_{1}^{'}$ and its higher order relatives first appear below its Néel temperature $T_{N} = 15 K$ . On the other hand, magnetic peaks indexed by $q_{2}$ appear only below the WFM transition temperature, $T_{WFM} \sim 8 K$ . The positions of $q_{1}^{'}$ and $q_{2}$ move with temperature, but at low temperatures they lock into $\sim 0.55 a^{*} \pm 0.002 b^{*}$ and $0.545 a^{*}$ , respectively. Furthermore, an intensity analysis reveals that the WFM behavior observed in ${TbNi}_{2} B_{2} C$ is associated with the magnetic peaks indexed by $q_{2}$ .

Received 31 July 2007

DOI:https://doi.org/10.1103/PhysRevB.77.144426

Authors & Affiliations

H. Kawano-Furukawa and H. Tsukagoshi

Graduate School of Humanities and Sciences, Ochanomizu University, Tokyo 112-8610, Japan

T. Nagata

Department of Physics, Ochanomizu University, Tokyo 112-8610, Japan

C. Kobayashi

Academic and Information Board, Ochanomizu University, Tokyo 112-8610, Japan

H. Yoshizawa

Neutron Science Laboratory, Institute for Solid State Physics, The University of Tokyo, Ibaraki 319-1106, Japan

H. Takeya

National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan

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Vol. 77, Iss. 14 — 1 April 2008

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Figure 1
(a) Temperature dependence of the longitudinal profiles of neutron diffraction around a nuclear Bragg position of (2 0 0). Each data set is shifted by $4 \times 10^{3}$ . (b) Temperature dependence of the lattice constants $a$ and $b$ through the tetragonal to the orthorhombic structural transition at $T_{N}$ .Reuse & Permissions
Figure 2
Results of magnetization measurements. (a) Temperature dependence of the magnetization at fields of 100 and 1000 Oe. The open and filled symbols denote the data recorded with increasing temperature after a zero field cooling process (ZFC) and with decreasing temperature in field (FCC), respectively. (b) Magnetization curves at 1.8, 6.0, 12, and 20 K. The data are recorded in a decreasing field from 5 T $(= 50 kOe)$ . In all measurements, external fields were applied parallel to the $a$ axis.Reuse & Permissions
Figure 3
Neutron diffraction profiles observed along $(h 0 2)$ at (a) 30, (b) 11, and (c) 1.25 K. (b) and (c) have grids that divide a region of $0 \leq h \leq 1$ into 20 and 11, respectively. The arrows indicate the positions where extra peaks were observed.Reuse & Permissions
Figure 4
(a) Temperature dependence of the magnetic profiles along the $h$ direction around the $(3 0 1) - 5 q$ position with $q \sim 0.55 a^{*}$ . [(b) and (c)] Temperature dependence of the peak positions and integrated intensities of $q_{1}$ and $q_{2}$ . For explanations of $q_{1}$ and $q_{2}$ , see the text.Reuse & Permissions
Figure 5
(Color online) (a) Temperature dependence of the contour plots of the magnetic intensity measured on the $(h k 0)$ planes around the $(3 1 0) - 5 q$ position. (b) Map of the temperature dependence of the peak positions (cooling data only). The black lines connect each data at 3.7 K with the origin (0 0). For detailed explanations, see the text.Reuse & Permissions
Figure 6
[(a) and (b)] Models for squared-up SDW magnetic structures with propagation vectors of $q_{1} = 11 / 20 a^{*}$ and $q_{2} = 6 / 11 a^{*}$ . The open circles indicate the Tb sites at nodes. [(c) and (d)] Observed intensity ratio $[I_{obs} / q^{2} L (θ) f^{2} (Q)]$ and magnetic structure factors ${| F_{M} (h k l) |}^{2}$ calculated for the models setting ferromagnetic $(↑, ↑)$ $(○)$ and antiferromagnetic $(↑, ↓)$ $(△)$ or (0, 0) $(◻)$ spins at each nodal position. In each figure, ${| F_{M} (h k l) |}^{2}$ is scaled to the intensity at the $h \sim 0.55$ position. In order to calculate the observed intensity, the background data at 30 K were first subtracted—except for (0 0 2) and $2 q$ ( $h \sim 0.9$ and 1.1) positions, where the crystallographic transition at $T_{N}$ leads to changes in nuclear intensities, so we subtracted 11 K data as background. (e) The observed intensity vs calculated intensity. The calculated intensity is given as $I_{mag} \propto {(1 / 20)}^{2} (0.24) {| F_{AFM}^{q_{1}} |}^{2} + {(1 / 11)}^{2} (0.76) {| F_{WFM}^{q_{2}} |}^{2}$ and was scaled at the $h \sim 0.55$ position. For detailed explanations, see the text.Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Weak ferromagnetism in ${TbNi}_{2} B_{2} C$

H. Kawano-Furukawa, H. Tsukagoshi, T. Nagata, C. Kobayashi, H. Yoshizawa, and H. Takeya

Phys. Rev. B 77, 144426 – Published 24 April 2008

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Physical Review B

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Weak ferromagnetism in TbNi2B2C

H. Kawano-Furukawa, H. Tsukagoshi, T. Nagata, C. Kobayashi, H. Yoshizawa, and H. Takeya

Phys. Rev. B 77, 144426 – Published 24 April 2008

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Weak ferromagnetism in ${TbNi}_{2} B_{2} C$