Cooling Field Dependence of Exchange Bias in Mn-Doped Metal- Organic Framework [NH 2 (CH 3 ) 2 ][Fe III Fe II (HCOO) 6 ].

Herein, an intriguing exchange bias (EB) effect manifesting itself from positive to negative with an increase in the cooling field ( H FC ) is reported in the single crystal of Mn-doped metal-organic framework (MOF) [NH 2 (CH 3 ) 2 ][Fe III Fe II (HCOO) 6 ] ( 1 ) by finely tuning the exchange interactions between the magnetic ions. Note that the doping ratio of Mn relative to the total metal ions is about 15%. Negative magnetization and EB below the compensation temperature were both observed in 1 , and the EB field ( H E ) changes its sign from positive to negative when H FC is larger than ∼10 kOe. The abnormal H FC dependence of EB can be interpreted explicitly by a combination of negative magnetization and couplings among the ions of Fe 3+ , Fe 2+ , and Mn 2+ with varying the H FC . This work demonstrates a tunable EB in MOFs, in favor of designing novel magnetic devices.