Layer buckling and absence of superconductivity in LaNiO2
/ Authors
S. Rathnayaka, S. Yano, K. Kawashima, J. Akimitsu, C. M. Brown, J. Neuefeind, D. L. U. O. Virginia, Department of Applied Physics, Charlottesville, Virginia
and 24 more authors
U.S.A. Neutron Group, N. Center, Hsinchu, Taiwan, R. D. P. D. O. Physics, Mathematics, A. University, Fuchinobe, Sagamihara, Kanagawa, J. I. F. C. Research, National Institute of Standards, Technology, Gaithersburg, Md., University of Maryland Department of Chemical Engineering, U. Delaware, Newark, De, Usa Current address- Intense Pulsed Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tn, USA.
/ Abstract
The recent observation of unconventional superconductivity in thin films of LaNiO2 (critical temperature, Tc~10 K) and in bulk single crystals of La3Ni2O7 (327) under pressure (Tc~80 K), has brought to light a long sought-after class of superconducting nickelates. Through structural measurements in the 327-system, it was shown that the absence of superconductivity is related to bending of the O-Ni-O bonds. Similarly, the bond bending may be linked to the absence of superconductivity in bulk LaNiO2. Neutron diffraction was used on bulk non-superconducting La(1-x)Sr(x)NiO(2) samples to show that the layers are naturally buckled, creating a Ni-O-Ni bond angle of 177 at 2 K and ambient pressure. The buckling angle increases to 170 on warming to room temperature. Furthermore, a broad paramagnetic continuum is observed that decreases in intensity on cooling from room temperature signaling a possible transition to a coherent state. However, no antiferromagnetic (AFM) peaks are detected, although enhancement of ferromagnetic (FM) correlations cannot be excluded.