Noncollinear spin order, field-induced transitions, and short-range correlations in CuSO(OH)

Prokhnenko, O.*; 金子 耕士   ; 田端 千紘; 赤木 満*; Lee, C.*; 山中 隆義*; 酒井 宏典   ; 廣瀬 雄介; Gazizulina, A.*; 常盤 欣文  ; 芳賀 芳範   ; 木俣 基; 藤田 全基*; 野尻 浩之*; Anovitz, L. M.*; Podlesnyak, A.*

Prokhnenko, O.*; Kaneko, Koji; Tabata, Chihiro; Akaki, Mitsuru*; Lee, C.*; Yamanaka, Takayoshi*; Sakai, Hironori; Hirose, Yusuke; Gazizulina, A.*; Tokiwa, Yoshifumi; Haga, Yoshinori; Kimata, Motoi; Fujita, Masaki*; Nojiri, Hiroyuki*; Anovitz, L. M.*; Podlesnyak, A.*

We report a comprehensive study of spin- quantum magnet brochantite, CuSO(OH), combining high-field thermodynamic measurements, polarized neutron diffraction, inelastic neutron scattering, and nuclear magnetic resonance spectroscopy. Using bulk magnetization and specific heat measurements we construct the magnetic - phase diagram for magnetic fields applied along main crystallographic directions. Polarized neutron diffraction reveals a noncollinear magnetic ground state confined to the ab plane. A field-induced transition is observed for magnetic fields in the ab plane whose critical field and character evolve continuously with field direction in the ab plane. The experimental results demonstrate that the ground-state and field-induced phases cannot be explained by a simple XXZ model with a single dominant exchange interaction and that weaker interchain and anisotropic interactions have to be taken into account. Our work establishes brochantite as a low-symmetry Cu-based quantum magnet with noncollinear order and complex field-induced behavior.