High-field Depinned Phase and Planar Hall Effect in the Skyrmion Host Gd2PdSi3

For the skyrmion-hosting intermetallic Gd2PdSi3 with centrosymmetric hexagonal lattice and triangular net of rare earth sites, we report a thorough investigation of the magnetic phase diagram. Our work reveals a magnetic phase with an isotropic value of the critical field for all orientations, where the magnetic ordering vector q is depinned from its preferred directions in the basal plane. The bulk nature of the skyrmion lattice and of other magnetic phases was evidenced by specific-heat measurements. Resistivity anisotropy, likely originating from partial gapping of the density of states along q in this Ruderman-Kittel-Kasuya-Yosida magnet, is picked up via the planar Hall effect (PHE). The PHE confirms the single-q nature of the magnetic order when the field is in the hexagonal plane, and allows one to detect the preferred directions of q. Several scenarios for the depinned phase, such as tilted conical order, are discussed on the basis of the data.