Finance

Physics

Charge (physics)

Magnetization

Crystallography

Magnetic field

Crystal structure

Superlattice

Phase transition

Magnetic structure

Order (exchange)

Charge ordering

Economics

Tetragonal crystal system

Chemistry

Materials science

Condensed matter physics

Charge density wave

Superconductivity

Quantum mechanics

Neutron diffraction

Journal of the Physical Society of Japan

Multiple transition phenomena in divalent Eu compound EuAl$_4$ with the tetragonal structure were investigated via the single-crystal time-of-flight neutron Laue technique. At 30.0 K below a charge-density-wave (CDW) transition temperature of $T_{\rm CDW}$ = 140 K, superlattice peaks emerge near nuclear Bragg peaks described by an ordering vector $q_{\rm CDW}$=(0 0 ${\delta}_c$) with ${\delta}_c{\sim}$0.19. In contrast, magnetic peaks appear at $q_2 = ({\delta}_2 {\delta}_2 0)$ with ${\delta}_2$ = 0.085 in a magnetic-ordered phase at 13.5 K below $T_{\rm N1}$ = 15.4 K. By further cooling to below $T_{\rm N3}$ = 12.2 K, the magnetic ordering vector changes into $q_1 = ({\delta}_1 0 0)$ with ${\delta}_1$ = 0.17 at 11.5 K and slightly shifts to ${\delta}_1$ = 0.194 at 4.3 K. No distinct change in the magnetic Bragg peak was detected at $T_{\rm N2}$=13.2 K and $T_{\rm N4}$=10.0 K. The structural modulation below $T_{\rm CDW}$ with $q_{\rm CDW}$ is characterized by the absence of the superlattice peak in the (0 0 $l$) axis. As a similar CDW transition was observed in SrAl$_4$, the structural modulation with $q_{\rm CDW}$ could be mainly ascribed to the displacement of Al ions within the tetragonal $ab$-plane. Complex magnetic transitions are in stark contrast to a simple collinear magnetic structure in isovalent EuGa$_4$. This could stem from different electronic structures with the CDW transition between two compounds.

Charge-Density-Wave Order and Multiple Magnetic Transitions in Divalent Europium Compound EuAl<sub>4</sub>

Charge-Density-Wave Order and Multiple Magnetic Transitions in Divalent Europium Compound EuAl4

Charge-Density-Wave Order and Multiple Magnetic Transitions in Divalent Europium Compound EuAl₄