Conferència a càrrec de Daniel Reta, University of Manchester, UK.
Resum:
Lanthanides have been extensively investigated for potential applications in quantum information processing and high-density data storage at the molecular and atomic scale; remarkable experimental achievements include reading and manipulating single nuclear spins exploiting atomic clock transitions for robust qubits, and most recently magnetic data storage in single atoms. Single molecule magnets (SMMs) display magnetic hysteresis of molecular origin – a magnetic memory effect and a prerequisite of data storage – and lanthanide examples have exhibited this phenomenon at the highest temperatures to date. However, in nearly 25 years since the landmark discovery of SMMs hysteresis temperatures have only increased from 4 K to ~14 K (using a consistent magnetic field sweep rate of ca. 20 Oe s –1 , though higher temperatures have been achieved by using very fast sweep rates, e.g. 30 K with 200 Oe s –1 ). Here we report a hexa-tert-butyldysprosocenium complex, [Dy(Cp ttt ) 2 ][B(C 6 F 5 ) 4 ] [1; Cp ttt = {C 5 H 2t Bu 3 -1,2,4}; t Bu = C(CH 3 ) 3 ], which shows magnetic hysteresis up to 60 K at 22 Oe s –1 . We observe a clear change in the relaxation dynamics at this temperature, which persists in magnetically diluted samples, suggesting that the origin of the hysteresis is the localised metal-ligand vibrational modes unique to dysprosocenium. Ab initio spin dynamics demonstrate that magnetic relaxation at high temperatures is due to local molecular vibrations, and thus indicate that with judicious molecular design, magnetic data storage in single molecules at temperatures above liquid nitrogen may become possible.
