TY  - JOUR
AU  - Kulbakov, A. A.
AU  - Sarkar, R.
AU  - Janson, O.
AU  - Dengre, S.
AU  - Weinhold, T.
AU  - Moshkina, E. M.
AU  - Portnichenko, P. Y.
AU  - Luetkens, H.
AU  - Yokaichiya, F.
AU  - Sukhanov, A. S.
AU  - Eremina, R. M.
AU  - Schlender, Ph.
AU  - Schneidewind, A.
AU  - Klauss, H.-H.
AU  - Inosov, D. S.
TI  - 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
JO  - Physical review / B
VL  - 103
IS  - 2
SN  - 2469-9950
CY  - Woodbury, NY
PB  - Inst.
M1  - FZJ-2021-00888
SP  - 024447
PY  - 2021
AB  - 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.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000612211100003
DO  - DOI:10.1103/PhysRevB.103.024447
UR  - https://juser.fz-juelich.de/record/890315
ER  -