Magnetic excitations affected by spin-lattice coupling in the $S=\frac{3}{2}$ triangular lattice antiferromagnet ${\mathrm{Ag}}_{2}{\mathrm{CrO}}_{2}$

Magnetic excitations affected by spin-lattice coupling in the $S = \frac{3}{2}$ triangular lattice antiferromagnet ${Ag}_{2} {CrO}_{2}$

Masaaki Matsuda, Sachith E. Dissanayake, Hiroyuki K. Yoshida, Masaaki Isobe, and Matthew B. Stone

Phys. Rev. B 102, 214411 – Published 9 December 2020

Abstract

${Ag}_{2} {CrO}_{2}$ is an $S = \frac{3}{2}$ triangular lattice antiferromagnet in which long-range magnetic order with a fivefold magnetic unit cell appears below the transition temperature ( $T_{N}$ ) of 24 K. The long-range magnetic order is accompanied by a structural transition. Inelastic neutron scattering experiments were performed to investigate the magnetic interactions, anisotropy, and correlations in this material. Above $T_{N}$ , diffuse scattering originating from the short-ranged magnetic correlations consistent with a $120^{\circ}$ structure was observed. The magnetic excitations below $T_{N}$ were reproduced reasonably well using a linear spin-wave model with further-neighbor interactions and easy-axis anisotropy, which are predicted to be due to a previously proposed spin-lattice coupling [Wang and Vishwanath, Phys. Rev. Lett. 100, 077201 (2008)].

Received 10 June 2020
Revised 25 November 2020
Accepted 30 November 2020

DOI:https://doi.org/10.1103/PhysRevB.102.214411

Physics Subject Headings (PhySH)

Frustrated magnetism Magnons

Antiferromagnets

Inelastic neutron scattering

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Masaaki Matsuda ¹, Sachith E. Dissanayake^1,*, Hiroyuki K. Yoshida², Masaaki Isobe ³, and Matthew B. Stone¹

¹Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
²Department of Physics, Hokkaido University, Sapporo 060-0810, Japan
³National Institute for Materials Science, Tsukuba, Ibaraki 305-0044, Japan

^*Present address: Department of Physics, Duke University, Durham, North Carolina 27708, USA.

Article Text (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 102, Iss. 21 — 1 December 2020

Reuse & Permissions

Access Options

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
Schematic structures of the ${CrO}_{2}$ plane of ${Ag}_{2} {CrO}_{2}$ in the trigonal ( $P \bar{3} m 1$ ) phase above $T_{N}$ ( $= 24$ K) (a) and monoclinic ( $C 2 / m$ ) phase below $T_{N}$ (b). The ${Cr}^{3 +}$ ions carry spins of $\frac{3}{2}$ . The collinear magnetic structure below $T_{N}$ is shown in (b). Magnetic interactions in the trigonal phase ( $J_{1}, J_{2}$ , and $J_{3}$ ) and in the monoclinic phase ( $J_{1}, J_{1}^{'}, J_{2}, J_{2}^{'}, J_{3}$ , and $J_{3}^{'}$ ) are shown in (a) and (b), respectively. The rhombus with dotted lines in (b) is the magnetic unit cell.
Reuse & Permissions
Figure 2
Contour maps of the inelastic neutron scattering intensity $S (| Q |, E)$ for ${Ag}_{2} {CrO}_{2}$ powder measured with $E_{i} = 15 meV$ at $T = 5$ , 20, 24 ( $= T_{N}$ ), 27.5, 100, and 230 K. The background intensities, measured with an empty cell at each temperature, were subtracted.
Reuse & Permissions
Figure 3
(a) Energy cuts of $S (| Q |, E)$ integrated with respect to $| Q |$ in the range of $1 \leq | Q | \leq 3 Å^{- 1}$ at $T = 5$ , 20, 24, 27.5, and 100 K. The intensities below $\sim 1.5$ meV originate from incoherent scattering. The broken line represents estimated background intensity. (b) $Q$ cuts of $S (| Q |, E)$ integrated with respect to energy in the range of $1.5 \leq E \leq 2.0$ meV measured with $E_{i} = 15 meV$ at $T = 5$ , 24, 27.5, 40, 60, and 100 K. The solid lines are results of fits to a Lorentzian function. For clarity, the intensities are shifted upward by multiples of 20 counts. The horizontal broken lines represent origins of intensities at higher temperatures.
Reuse & Permissions
Figure 4
Temperature dependence of the parameters fitted with a Lorentizan function using the inelastic data shown in Fig. 3. (a) Inverse $κ$ , which corresponds to a quantity proportional to the correlation length, as a function of temperature. (b) Peak intensity $A$ as a function of temperature. The inset shows the temperature dependence of the magnetic Bragg peak (1/5, 1/5, 0) measured on a neutron powder diffractometer [17].
Reuse & Permissions
Figure 5
Results of linear spin-wave calculations performed using spinw [25]. (a), (c), and (e) Spin-wave dispersions along the high-symmetry directions, which are specified in the inset of (a). (b), (d), and (f) Powder-averaged magnetic excitations calculated with the same parameters in (a), (c), and (e), respectively. In the calculations, the instrumental energy resolution was convoluted. The magnetic interaction and anisotropy parameters used for the calculations are listed in Table 1. Calculations were performed with Parameter set I [(a) and (b)], II [(c) and (d)], and III [(e) and (f)].
Reuse & Permissions

Physical Review B

covering condensed matter and materials physics

Magnetic excitations affected by spin-lattice coupling in the $S = \frac{3}{2}$ triangular lattice antiferromagnet ${Ag}_{2} {CrO}_{2}$

Masaaki Matsuda, Sachith E. Dissanayake, Hiroyuki K. Yoshida, Masaaki Isobe, and Matthew B. Stone

Phys. Rev. B 102, 214411 – Published 9 December 2020

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Physical Review B

covering condensed matter and materials physics

Magnetic excitations affected by spin-lattice coupling in the S=32 triangular lattice antiferromagnet Ag2CrO2

Masaaki Matsuda, Sachith E. Dissanayake, Hiroyuki K. Yoshida, Masaaki Isobe, and Matthew B. Stone

Phys. Rev. B 102, 214411 – Published 9 December 2020

Abstract

Physics Subject Headings (PhySH)

Authors & Affiliations

Article Text (Subscription Required)

References (Subscription Required)

Issue

Access Options

Authorization Required

Other Options

Download & Share

Images

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Log In

Search

Article Lookup

Paste a citation or DOI

Enter a citation

Magnetic excitations affected by spin-lattice coupling in the $S = \frac{3}{2}$ triangular lattice antiferromagnet ${Ag}_{2} {CrO}_{2}$