Charge-density-wave order and multiple magnetic transitions in divalent europium compound EuAl

Kaneko, Koji   ; Kawasaki, Takuro   ; Nakamura, Ai*; Munakata, Koji*; Nakao, Akiko*; Hanashima, Takayasu*; Kiyanagi, Ryoji  ; Ohara, Takashi   ; Hedo, Masato*; Nakama, Takao*; Onuki, Yoshichika*

Multiple transition phenomena in divalent Eu compound EuAl with the tetragonal structure were investigated via single crystal time-of-flight neutron Laue technique. At 30 K below a charge-density-wave (CDW) transition, superlattice peaks emerge near nuclear Bragg peaks described by an ordering vector = (0 0 ). In contrast, magnetic peaks appear at with = 0.09 below = 15.4 K, and moves to with = 0.19 below =12.2 K, whereas no distinct change in the magnetic Bragg peak was detected at and . The structural modification with is characterized by an absence of the superlattice peak in (0 0 ). Considering an absence of splitting in magnetic peaks along , the structural transition is mainly ascribed to a displacement of Al ions within the tetragonal -plane. Complex incommensurate magnetic transitions are in stark contrast to a simple collinear commensurate structure in isovalent EuGa. This could stem from incompatible electronic structures with the CDW transition between two compounds.