High-sensitivity vector magnetometer for measuring magnetic torque at low temperatures

Abstract

We present a fully automated vector vibrating-sample magnetometer where the sample can be rotated against the applied magnetic field Hap, so that the angular dependence of the longitudinal, Mlong, and transversal, Mtrans, components of M with respect to Hap on the rotation plane are determined. The magnetic field range is ±20kOe and temperature ranges between 4.2 and 340 K. The resolution is better than 2×10−7emu and the sensitivity is 5×10−6emu. Standard hysteresis loop measurements are possible as well. As examples of its capability we display torque curves performed at low temperatures in a [Ho8Lu15]50 superlattice and in a 60-nm-thick Terfenol-D thin film.

Spin-flop transition driven by competing magnetoelastic anisotropy terms in a spin-spiral antiferromagnet

“…High-precision vector magnetic torque experiments [20] revealed that Ho undergoes an unexpected field-induced inplane SFT, which was originally attributed to competing magnetoelastic (MEL) anisotropy [21] terms. The existence of a fully symmetric sixfold MEL coefficient λ 66 , which gives rise to the sixfold modulation of the α strains ε α1 (isotropic volume expansion) and ε α2 (tetragonal distortion of the hexagonal cell), originates a 12-fold MEL-induced magnetic anisotropy energy (MAE) constant K 12 12 as experimentally confirmed in bulk holmium [22].…”

Universal scaling of the magnetic anisotropy in two-dimensional rare-earth layers

“…Data recorded by this apparatus have significantly contributed to a better understanding of the influence that strain-induced magnetoelastic (MEL) terms [29,38,40] have upon the MAE in nanosystems and to demonstrate the anisotropy of the magnetization vector [41]. Experimental details on sample rotation and torque experiments can be found elsewhere [29,38,39,41]. The magnetic torque L k reads as L k = −M ⊥ (φ)H [29], where H is the applied magnetic field, M ⊥ is the transversal component with respect to H of the total magnetization M, and φ is the crystal angle, which is also obtained from the M in-plane components [39].…”

“…Experimental details on sample rotation and torque experiments can be found elsewhere [29,38,39,41]. The magnetic torque L k reads as L k = −M ⊥ (φ)H [29], where H is the applied magnetic field, M ⊥ is the transversal component with respect to H of the total magnetization M, and φ is the crystal angle, which is also obtained from the M in-plane components [39]. L k is typically investigated for a field range of μ 0 H = 1.5-2 T, for which a forced ferromagnetic (FM) state is formed.…”

“…Magnetic torque measurements were carried out in a vector vibrating sample magnetometer [39]. Data recorded by this apparatus have significantly contributed to a better understanding of the influence that strain-induced magnetoelastic (MEL) terms [29,38,40] have upon the MAE in nanosystems and to demonstrate the anisotropy of the magnetization vector [41].…”

“…Both SLs were grown by a molecular beam epitaxy technique in a Balzers UMS630 facility, with a base pressure of better than 2 × 10 −10 mbar and deposited onto epi-polished (1120)-oriented Al 2 O 3 substrates, following well-established growth techniques [35,36]. This procedure ensures that the Dy, Sc, Ho, and Lu metallic species, which all crystallize in the hexagonal-closed-packed (hcp) structure [30], grow with the c direction of the hcp lattice structure normal to the deposition plane [35,36], forming high-quality single crystals [37,38].Magnetic torque measurements were carried out in a vector vibrating sample magnetometer [39]. Data recorded by this apparatus have significantly contributed to a better understanding of the influence that strain-induced magnetoelastic (MEL) terms [29,38,40] have upon the MAE in nanosystems and to demonstrate the anisotropy of the magnetization…”