Magnetic tri-axial orientation in (Y1−xErx)2Ba4Cu7O15−y superconductors

► (Y1-xErx)2Ba4Cu7O15-y [(Y,Er)247] was synthesized for clarifying a magnetic role of Er ion. ► The three magnetization axes of (Y,Er)247 were obtained from tri-axial orientation using a modulated rotation magnetic field. ► Magnetic anisotropy of Er ion is roughly ten times higher than that for Y247 at room temperature. ► Importance of rare-earth ions was shown for reduction of required magnetic fields in the tri-axial magnetic orientation.