Model of ultrafast demagnetization driven by spin-orbit coupling in a photoexcited antiferromagnetic insulator Cr2O3

Abstract

We theoretically study the dynamic time evolution following laser pulse pumping in an antiferromagnetic insulator Cr2O3. From the photoexcited high-spin quartet states to the long-lived low-spin doublet states, the ultrafast demagnetization processes are investigated by solving the dissipative Schrödinger equation. We find that the demagnetization times are of the order of hundreds of femtosecond, in good agreement with recent experiments. The switching times could be strongly reduced by properly tuning the energy gaps between the multiplet energy levels of Cr 3+ . Furthermore, the relaxation times also depend on the hybridization of atomic orbitals in the first photoexcited state. Our results suggest that the selective manipulation of electronic structure by engineering stress-strain or chemical substitution allows effective control of the magnetic state switching in photoexcited insulating transition-metal oxides.

Ultrafast photoinduced dynamics in Prussian blue analogues

“…It is known that the local spin-configuration on Cr III sites in the ground state gives S = 3/2 and that the first excited state corresponds to one of the electrons flipped, which in a local picture corresponds to S = 1/2. In molecules 5,155 and solids 156,157 this state can be populated within a few 100 fs. Johansson et al interpreted the fast change in fs-MO signal as due to local spinflips on the Cr sites after photoexcitation, which in turn will affect the superexchange interaction.…”

Increased Excited State Metallicity in Neutral Cr2On Clusters (n < 5) upon Sequential Oxidation

“…The ultimate speed at which its magnetic states can be manipulated is of key importance due to its attractive potential for use in spintronic heterostructures and magnetoelectronic devices requiring spin polarization, such as magnetic tunnel junctions and spin valves . The photodriven process of (de)­magnetization and optical spin transport can be manipulated with light on the femtosecond time scale, but follows a complex route of intermediate states accompanying changes in spin and lattice parameters, and is not fully understood . Despite its relevance to industrial technology, controlling the magnetic states in chromium oxides requires more detailed information on oxygen-dependent electronic state dynamics and electron transport.…”

“…The properties of chromium oxides are driven partially by superexchange coupling, , suggesting the charge-transport processes are adiabatic in nature. Manipulation of spin in antiferromagnetic (AF) Cr 2 O 3 bulk materials follows several relaxation channels dependent on excitation energy, proceeding over hundreds of femtoseconds to picoseconds. ,, However, the mixing of Cr and O electrons and their effect on the lifetimes of accessible magnetic states are still not well understood and may improve the manipulation of chromium oxide materials.…”

“…6 The photodriven process of (de)magnetization and optical spin transport can be manipulated with light on the femtosecond time scale, but follows a complex route of intermediate states accompanying changes in spin and lattice parameters, and is not fully understood. 7 Despite its relevance to industrial technology, controlling the magnetic states in chromium oxides requires more detailed information on oxygen-dependent electronic state dynamics and electron transport.…”

Manipulation of Antiferromagnetic Spin Using Tunable Parasitic Magnetization in Magnetoelectric Antiferromagnet

“…Since the 180° control of antiferromagnetic spin and antiferromagnetic single domain state obtained by it are an indispensable piece for the expression of the superior properties of AFMs, the easier way has been highly desired. In additions to the 180° control availability of antiferromagnetic spin, recently many fundamental findings such as observations of the spin Seebeck effect, discovery of curious spin‐transport properties, and investigation of ultra‐fast spin response have been reported for Cr 2 O 3 . Cr 2 O 3 has received an increasing attention as a key material for antiferromagnetic spintronics.…”