%0 Journal Article
%A Nair, Harikrishnan
%A Fu, Zhendong
%A Voigt, Jörg
%A Su, Yixi
%A Brückel, Thomas
%T Approaching the true ground state of frustrated A-site spinels: A combined magnetization and polarized neutron scattering study
%J Physical review / B
%V 89
%N 17
%@ 1098-0121
%C College Park, Md.
%I APS
%M FZJ-2014-05836
%P 174431
%D 2014
%X 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.
%F PUB:(DE-HGF)16
%9 Journal Article
%U <Go to ISI:>//WOS:000336752500005
%R 10.1103/PhysRevB.89.174431
%U https://juser.fz-juelich.de/record/172356