Neutron diffraction study on magnetic structures in a La1.37Sr1.63Mn2O7single crystal under hydrostatic pressures of up to 0.8 GPa

Magnetic structures in La${}_{1.37}$Sr${}_{1.63}$Mn${}_{2}$O${}_{7}$ single crystal under hydrostatic pressures of up to 0.8 GPa are investigated by neutron diffraction measurements to determine the magnetic phase diagram under hydrostatic pressure. The ground state is found to be a ferromagnetic (FM${}_{\mathrm{uniaxial}}$) structure under hydrostatic pressures of up to 0.8 GPa, in which the magnetic moments of Mn ions are parallel to the $c$ axis. Under hydrostatic pressures of $P$ 0.75 GPa, the FM${}_{\mathrm{uniaxial}}$ structure changes to a canted antiferromagnetic (CAFM) structure at approximately 70 K and the CAFM structure directly changes to a paramagnetic (PM) structure at approximately 120 K. Under hydrostatic pressures of 0.75 GPa \ensuremath{\le} $P$ \ensuremath{\le} 0.8 GPa, the FM${}_{\mathrm{uniaxial}}$ structure changes to a CAFM structure at approximately 70 K, and the CAFM structure changes to a PM structure at approximately 120 K via an antiferromagnetic (AFM${}_{\mathrm{planar}}$) structure at approximately 95 K in which the magnetic moment lies in the $ab$ plane. The relationship between the magnetic structure and the distortion of the MnO${}_{6}$ octahedra is also discussed.