Understanding the microscopic mechanisms of energy exchange between lattice and spin degrees of freedom is fundamental to the development of next-generation spintronic and magnonic devices. Here we employ transient absorption (TA) spectroscopy to investigate the nonequilibrium spin dynamics in antiferromagnetic cobalt oxide films following photoexcitation. We demonstrate that the TA features associated with the $d\text{−}d$ transitions of transition metal ions act as an effective thermometer for tracking transient spin temperature. Below the Néel temperature, we observe a slow, nanosecond-scale rise in spin temperature, which we attribute to energy transfer from the photoheated lattice to the spin subsystem. Our analysis reveals that the spin-lattice coupling coefficient follows a $T^3$ power-law dependence, consistent with a microscopic model where the energy transfer rate is governed by the thermal occupancy of magnons in the presence of a large hot phonon population. These findings establish $d\text{−}d$ transitions as a sensitive spectroscopic probe for nonthermal spin dynamics and provide fundamental insights into the scaling laws governing spin-lattice equilibration in antiferromagnetic oxides

Close

PrevNext

View figure in article

• Magnons
• Magnetic insulators
• Transient absorption spectroscopy