%0 Journal Article
%A Kulbakov, A. A.
%A Sarkar, R.
%A Janson, O.
%A Dengre, S.
%A Weinhold, T.
%A Moshkina, E. M.
%A Portnichenko, P. Y.
%A Luetkens, H.
%A Yokaichiya, F.
%A Sukhanov, A. S.
%A Eremina, R. M.
%A Schlender, Ph.
%A Schneidewind, A.
%A Klauss, H.-H.
%A Inosov, D. S.
%T Destruction of long-range magnetic order in an external magnetic field and the associated spin dynamics in Cu 2 GaBO 5 and Cu 2 AlBO 5 ludwigites
%J Physical review / B
%V 103
%N 2
%@ 2469-9950
%C Woodbury, NY
%I Inst.
%M FZJ-2021-00888
%P 024447
%D 2021
%X The quantum spin systems Cu2MBO5 (M = Al, Ga) with the ludwigite crystal structure consist of astructurally ordered Cu2+ sublattice in the form of three-leg ladders, interpenetrated by a structurally disorderedsublattice with a statistically random site occupation by magnetic Cu2+ and nonmagnetic Ga3+ or Al3+ ions. Amicroscopic analysis based on density-functional-theory calculations for Cu2GaBO5 reveals a frustrated quasitwo-dimensional spin model featuring five inequivalent antiferromagnetic exchanges. A broad low-temperature11B nuclear magnetic resonance points to a considerable spin disorder in the system. In zero magnetic field,antiferromagnetic order sets in below TN ≈ 4.1 K and ∼2.4 K for the Ga and Al compounds, respectively. Fromneutron diffraction, we find that the magnetic propagation vector in Cu2GaBO5 is commensurate and lies on theBrillouin-zone boundary in the (H0L) plane, qm = (0.45, 0, −0.7), corresponding to a complex noncollinearlong-range ordered structure with a large magnetic unit cell. Muon spin relaxation is monotonic, consisting of afast static component typical for complex noncollinear spin systems and a slow dynamic component originatingfrom the relaxation on low-energy spin fluctuations. Gapless spin dynamics in the form of a diffuse quasielasticpeak is also evidenced by inelastic neutron scattering. Most remarkably, application of a magnetic field above1 T destroys the static long-range order, which is manifested in the gradual broadening of the magnetic Braggpeaks. We argue that such a crossover from a magnetically long-range ordered state to a spin-glass regime mayresult from orphan spins on the structurally disordered magnetic sublattice, which are polarized in magnetic fieldand thus act as a tuning knob for field-controlled magnetic disorder.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000612211100003
%R 10.1103/PhysRevB.103.024447
%U https://juser.fz-juelich.de/record/890315