Dresden 2020 – scientific programme
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MA: Fachverband Magnetismus
MA 21: Ultrafast Magnetization II
MA 21.3: Talk
Tuesday, March 17, 2020, 10:00–10:15, HSZ 101
Ultrafast excitation across the transition between antiferromagnetic phases. — •Yoav William Windsor1, Daniela Zahn1, Sang-Eun Lee1, Kristin Kliemt2, Cornelius Krellner2, and Laurenz Rettig1 — 1Fritz-Haber-Institut der MPG (DE) — 2Goethe-Universität Frankfurt (DE)
Antiferromagnetic spintronics are a promising route towards more efficient and stable devices. The prospect of employing antiferromagnets in devices opens new functionality pathways through properties that are not available with ferromagnets. One promising direction is light induced variations of the long-range spin arrangement.
Here we study Ho 4f spin dynamics in HoRh2Si2, a material with two antiferromagnetic phases with different spin arrangements: a high-T phase, in which all spins align (anti)parallel to [001], and a low-T phase in which they tilt by ∼30∘ away from [001]. This is a change in the local 4f anisotropy, caused by variations in the crystal field.
We excite the low-T phase with a femtosecond optical laser pulse and probe the antiferromagnetic order’s response using time-resolved resonant X-ray diffraction. Using the anisotropy of magnetic scattering, we decouple demagnetization dynamics from spin-tilting dynamics. These dynamics are distinctly different, demonstrating that AF order and collective spin rearrangement do not evolve together upon excitation (unlike upon heating). We identify two regimes: excitation within the low-T phase, and exciting from low-T to the high-T phase. Implications on the crystal field and its relation to the RKKY coupling between the Ho 4f moments will be discussed.