Ultrafast Optically Induced Ferromagnetic State in an Elemental Antiferromagnet

We present evidence for an ultrafast optically induced ferromagnetic alignment of antiferromagnetic Mn in Co/Mn multilayers. We observe the transient ferromagnetic signal at the arrival of the pump pulse at the Mn L3 resonance using x-ray magnetic circular dichroism in reflectivity. The timescale of the effect is comparable to the duration of the excitation and occurs before the magnetization in Co is quenched. Theoretical calculations point to the imbalanced population of Mn unoccupied states caused by the Co interface for the emergence of this transient ferromagnetic state

Thermal and Light Induced Spin Crossover Characteristics of a Functional Iron II Complex at Submonolayer Coverage on HOPG

Studies on the spin state switching characteristics of surface bound thin films of spin crossover SCO complexes are of interest to harness the device utility of the SCO complexes. Molecule substrate interactions govern the SCO of surface bound films in direct contact with the underlying substrates. In this study, we elucidate the role of molecule substrate interactions on the thermal and light induced spin state switching characteristics of a functional SCO complex [Fe H2B pz 2 2COOC12H25 bipy] pz pyrazole, C12 bpy dodecyl[2,2 amp; 8242; bipyridine] 5 carboxylate deposited at a submonolayer coverage on a highly oriented pyrolytic graphite HOPG substrate. A spin state coexistence of 42 low spin LS and 58 high spin HS is observed for the 0.4 ML deposit of the complex at 40 K, in contrast to the complete spin state switching observed in the bulk and in SiOx bound 10 nm thick films. Cooling the sample to 10 K results in a decrease of the LS fraction to 36 , attributed to soft X ray induced excited spin state trapping SOXIESST . Illumination of the sample with a green light amp; 955; 520 nm at 10 K caused the LS to HS switching of the remaining 36 LS complexes, by a process termed light induced excited spin state trapping LIESST . The mixed spin state in the submonolayer coverage of [Fe H2B pz 2 2COOC12H25 bipy] highlights the role of molecule HOPG substrate interactions in tuning the thermal SCO characteristics of the complex. The 100 HS state obtained after light irradiation indicates the occurrence of efficient on surface light induced spin switching, encouraging the development of light addressable molecular devices based on SCO complexe