Qing'An Li

Publications (2)7.37 Total impact

• Article: Antiferromagnetic Domain Structure in Bilayer Manganite

  M. García-Fernández, S. B. Wilkins, Ming Lu, Qing'an Li, K. E. Gray, H. Zheng, J. F. Mitchell, Daniel Khomskii
  [show abstract] [hide abstract]
  ABSTRACT: We report a novel soft x-ray nanodiffraction study of antiferromagnetic domains in the strongly correlated bylayer manganite La$_{0.96}$Sr$_{2.04}$Mn$_{2}$O$_{7}$. We find that the antiferromagnetic domains are quenched, forming a unique domain pattern with each domain having an intrinsic memory of its spin direction, and with associated domain walls running along crystallographic directions. This can be explained by the presence of crystallographic or magnetic imperfections locked in during the crystal growth process which pin the antiferromagnetic domains. The antiferromagnetic domain pattern shows two distinct types of domain. We observe, in one type only, a periodic ripple in the manganese spin direction with a period of approximately 4 \micro\meter. We propose that the loss of inversion symmetry within a bilayer is responsible for this ripple structure through a Dzyaloshinskii-Moriya-type interaction.
  02/2013;
• Source

  Available from: John F. Mitchell

  Article: Reentrant orbital order and the true ground state of LaSr2Mn2O7.

  Qing'An Li, K E Gray, H Zheng, H Claus, S Rosenkranz, S Nyborg Ancona, R Osborn, J F Mitchell, Y Chen, J W Lynn
  [show abstract] [hide abstract]
  ABSTRACT: Contrary to conventional wisdom, our purified La 2-2x Sr 1+2x Mn2O7 crystals exhibit CE-type orbital and charge order as the low-temperature ground state for a hole doping level h=0.5. For small deviations from h=0.5, the high-temperature CE phase is replaced at low temperatures by an A-type antiferromagnet without coexistence. Larger deviations result in a lack of CE order at any temperature. Thus, small inhomogeneities in cation or oxygen composition could explain why others commonly see this reentrance with coexistence.
  Physical Review Letters 05/2007; 98(16):167201. · 7.37 Impact Factor