Regensburg 2022 – scientific programme

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MA: Fachverband Magnetismus

MA 4: Disordered Magnetic Materials

MA 4.1: Talk

Monday, September 5, 2022, 09:30–09:45, H47

Destruction of long-range magnetic order in the Cu₂GaBO₅ ludwigite in a magnetic field — A. Kulbakov¹, R. Sarkar¹, O. Janson², S. Dengre¹, E. M. Moshkina³, P. Y. Portnichenko¹, H. Luetkens⁴, F. Yokaichiya⁵, A. S. Sukhanov^1,6, R. M. Eremina⁷, A. Schneidewind⁸, H.-H. Klauss¹, A. Korshunov⁹, and •D. S. Inosov¹ — ¹TU Dresden, Germany — ²IFW Dresden, Germany — ³Krasnoyarsk, Russia — ⁴PSI, Villigen, Switzerland — ⁵HZB, Berlin, Germany — ⁶MPI CPfS, Dresden, Germany — ⁷Kazan, Russia — ⁸JCNS @ MLZ, Forschungszentrum Jülich, Germany — ⁹ESRF, Grenoble, France

The quantum spin system Cu₂GaBO₅ with the ludwigite structure consists of a structurally ordered Cu²⁺ sublattice interpenetrated by a disordered sublattice with a random site occupation by magnetic Cu²⁺ and nonmagnetic Ga³⁺. In zero magnetic field, antiferromagnetic long-range order with the propagation vector q_m = (0.45, 0, 0.7) sets in below T_N = 4.1 K, corresponding to a complex noncollinear structure with a large magnetic unit cell. Gapless spin dynamics in the form of a diffuse quasielastic peak is evidenced by neutron scattering. Remarkably, a magnetic field of ∼1 T destroys the static long-range order, which is manifested in the gradual broadening of magnetic Bragg peaks. Such a crossover to a spin-glass regime may result from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic field and act as a tuning knob for field-controlled magnetic disorder. For details, see Phys. Rev. B 103, 024447 (2021).