Exploring metamagnetism of single crystallineEuNiGe3by neutron scattering

Abstract

We present here a neutron diffraction study, both in zero field and as a function of magnetic field, of the magnetic structure of the tetragonal intermetallic EuNiGe 3 on a single crystalline sample. This material is known to undergo a cascade of transitions, first at 13.2 K towards an incommensurate modulated magnetic structure, then at 10.5 K to an equal moment, yet undetermined, antiferromagnetic structure. We show here that the low temperature phase presents a spiral moment arrangement with wave-vector k = ( 1 4 , δ, 0). For a magnetic field applied along the tetragonal c-axis, the square root of the scattering intensity of a chosen reflection matches very well the complex metamagnetic behavior of the magnetization along c measured previously. For the magnetic field applied along the b-axis, two magnetic transitions are observed below the transition to a fully polarized state.

Helical spin order in EuFe2As2 and EuRbFe4As4 single crystals

“…In samples studied in this work (Fig. 4h) the metamagnetic transition occurs at µ 0 H ≈ 0.5 − 0.7 T, which is about a half of the saturation magnetization in ab-planes µ 0 H x S ≈ 1.25 T. At last, we notice that helicity is was confirmed for a variety of europium-based anti-ferromagnets: [37][38][39][40] EuCo 2 P 2 , EuCo 2 As 2 , and EuNiGe 3 . Thus, consideration of helical spin ordering in studied samples is fairly justified.…”

Spiral plane flops in frustrated helimagnets in external magnetic field

“…EuNiGe 3 is a helimagnet with equally possible spiral vectors k = ( 1 4 , δ, 0), ( 1 4 , −δ, 0), and (δ, 1 4 , 0) allowed by the tetragonal symmetry, where δ = 0.05. 19 Magnetodipolar interaction is expected to be very important in this material because exchange constants are rather small and Eu 2+ ions are in a spherically symmetric state with L = 0 and S = 7/2. 19 It can be shown 20 that dipolar forces make the spiral plane to be perpendicular to k in agreement with experimental observations.…”

“…19 Magnetodipolar interaction is expected to be very important in this material because exchange constants are rather small and Eu 2+ ions are in a spherically symmetric state with L = 0 and S = 7/2. 19 It can be shown 20 that dipolar forces make the spiral plane to be perpendicular to k in agreement with experimental observations. It is believed that a small Dzyaloshinskii-Moriya interaction is responsible for the finite δ.…”

“…21 Magnetic field directed along a and b tetragonal axes results in the spiral plane flop accompanied with changing k by another equivalent spiral wave vector. 19 Then, the theory presented above should be modified to describe such flops (as it is done in Ref. 22 for a collinear antiferromagnet).…”

Anomalous Hall Effect in Antiferromagnet EuNiGe3 with the Rashba-type Tetragonal Structure

“…The present purpose is to investigate an effect of the magnetic field direction on the Hall resistivity in EuNiGe 3 . Eu ions of EuNiGe 3 are divalent (L = 0, S = J = 7/2) and order antiferromagnetically below the Néel temperature T N = 13 K, with the helical structure [12][13][14].…”