Torque magnetometry study of magnetically ordered state and spin reorientation in the quasi-one-dimensionalS=12Heisenberg antiferromagnetCuSb2O6

Abstract

Antiferromagnetically ordered state of monoclinic quasi-one-dimensional S = 1/2 Heisenberg antiferromagnet CuSb 2 O 6 was studied combining torque magnetometry with phenomenological approach to magnetic anisotropy. This system is known to have a number of different twins in monoclinic β phase which differ in orientation of the two CuO 6 octahedra in unit cell resulting in different orientation of magnetic axes with respect to crystal axes for each twin. We performed torque measurements in magnetic fields H ≤ 0.8 T on a sample where certain type of twin was shown to be dominant by ESR spectroscopy. The measured data reveal that easy axis is the crystallographic b axis for this sample. Phenomenological magnetocrystalline anisotropy energy invariant to crystal symmetry operations was used to model spin axis direction in zero and finite magnetic field. Our model reproduces the value of the spin flop field H SF = 1.25 T found in literature. Combination of this approach with our torque results shows that the spin axis will flop in the direction of the maximal value of measured g tensor when magnetic field H > H SF is applied along easy axis direction. Our analysis of magnetocrystalline anisotropy energy predicts two possibilities for the easy axis direction in this system, b or a, connected to different crystallographic twins that can be realized in CuSb 2 O 6 . These results offer possibility to reconcile different reports of easy axis direction found in literature for this system and also nicely demonstrate how combination of torque magnetometry and phenomenological approach to magnetic anisotropy can be used to determine the value of the spin flop field and the direction of spin axis in antiferromagnets in both H < H SF and H > H SF by performing measurements in fields significantly smaller than H SF .

Lattice dynamics of ASb2O6 ( A=Cu , Co) with trirutile structure

“…Perhaps the most studied material of this class is the spin-1/2 quantum spin chain CuSb 2 O 6 . [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18] In this material, the Cu 2+ spins show a 3D magnetic order below T 3D N ∼ 8.5 K. The magnetic susceptibility curve has a broad maximum at about 60 K, being well modelled by a 1D Bonner and Fisher model 19 with an Heisenberg exchange coupling strength J ∼ −100 K between S = 1/2 spins. 2, 5,6,[8][9][10][11][12]15 This value of J has been associated with antiferromagnetic Cu-O-O-Cu superexchange interactions along the [1 1 0] and [1 -1 0] directions for Cu ions at z = 0 and z = 1/2, respectively [see Fig.…”

Probing magnetic anisotropy in Kagome antiferromagnetic Mn$_3$Ge with torque magnetometry

“…III. On the other hand, from the A 2 component we can obtain the susceptibility anisotropy ∆χ ≡ χ ab − χ c , where χ c and χ ab are the out-of-and in-plane susceptibilities, respectively, because the field-induced magnetization produces a torque equal to 1 2 ∆χH 2 sin 2θ [48,49]. In Fig.…”

Site-Specific Spin Reorientation in Antiferromagnetic State of Quantum System SeCuO$_3$

“…Specifically, torque magnetometry measurements can be employed to determine the MAE shape and also to study the spin axis reorientation in a finite magnetic field. We have successfully used this approach previously to study the magnetocrystalline anisotropy in a uniaxial antiferromagnet [21], but also in antiferromagnets with higher symmetries and multiple antiferromagnetic domains [22,23].…”