Unusual E-type Antiferromagnetic (AFM) Structure Found

While layered ruthenate materials are well known to display an array of exciting phenomena such as metal-insulator transitions (MIT), spin-orbital ordering, exotic superconductivity, and quantum criticality, Dalgis Mesa, Jiandi Zhang, Rongying Jin, and Ward Plummer have found an unusual E-type antiferromagnetic (AFM) structure in Mn-substituted Sr₃Ru₂O₇ (x = 0.16). They found that this layered ruthenate behaves as a quasi two-dimensional (2D) antiferromagnet with in-plane (ab) long-range ordering but only single bilayer (5-6Å) ferromagnetic correlations along the c direction bellow T_N = 78 K. Such Mn-induced magnetic structure is unusual because the critical behavior of the staggered magnetization (i.e. the AFM order parameter) does not reflect the expected behavior of a 2D magnetic phase transition (Mesa et al., Physical Review B 85, 180410(R) (2012)]. The work was done in collaboration with scientists at Oak Ridge National Laboratory.