Approaching the true ground state of frustrated A-site spinels: A combined magnetization and polarized neutron scattering study

Article

关键词: TEMPERATURE-DEPENDENCE;    CATION DISTRIBUTION;    ORDER;    GLASS;    DIFFRACTION;    DISORDER;    BEHAVIOR;    LIQUID;   

DOI  :  10.1103/PhysRevB.89.174431

来源: SCIE

【 摘 要 】

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 Lande 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 approximate to 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 antiferro magnetic 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.

【 授权许可】

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