TY  - JOUR
AU  - Nair, Harikrishnan
AU  - Fu, Zhendong
AU  - Voigt, Jörg
AU  - Su, Yixi
AU  - Brückel, Thomas
TI  - Approaching the true ground state of frustrated A-site spinels: A combined magnetization and polarized neutron scattering study
JO  - Physical review / B
VL  - 89
IS  - 17
SN  - 1098-0121
CY  - College Park, Md.
PB  - APS
M1  - FZJ-2014-05836
SP  - 174431
PY  - 2014
AB  - We re-investigate the magnetically frustrated, diamond-lattice-antiferromagnet spinels FeAl2O4 and MnAl2O4 using magnetization measurements and diffuse scattering of polarized neutrons. In FeAl2O4, macroscopic measurements evidence a “cusp” in zero field-cooled susceptibility around 13 K. Dynamic magnetic susceptibility and memory effect experiments provide results that do not conform with a canonical spin-glass scenario in this material. Through polarized neutron-scattering studies, absence of long-range magnetic order down to 4 K is confirmed in FeAl2O4. By modeling the powder averaged differential magnetic neutron-scattering cross section, we estimate that the spin-spin correlations in this compound extend up to the third nearest-neighbor shell. The estimated value of the Landé g factor points towards orbital contributions from Fe2+. This is also supported by a Curie-Weiss analysis of the magnetic susceptibility. MnAl2O4, on the contrary, undergoes a magnetic phase transition into a long-range ordered state below ≈40 K, which is confirmed by macroscopic measurements and polarized neutron diffraction. However, the polarized neutron studies reveal the existence of prominent spin fluctuations co-existing with long-range antiferromagnetic order. The magnetic diffuse intensity suggests a similar short-range order as in FeAl2O4. Results of the present work support the importance of spin-spin correlations in understanding magnetic response of frustrated magnets like A-site spinels which have predominant short-range spin correlations reminiscent of the “spin-liquid” state.
LB  - PUB:(DE-HGF)16
UR  - <Go to ISI:>//WOS:000336752500005
DO  - DOI:10.1103/PhysRevB.89.174431
UR  - https://juser.fz-juelich.de/record/172356
ER  -