The antiferromagnetic to ferromagnetic phase transition in FeRh can be induced globally by either heating the material above its phase transition temperature or applying a combination of external stimuli (such as mechanical strain, electric/magnetic fields) on the material preheated close to its transition temperature. On the other hand, to locally induce this phase transition is more desirable for applications and requires a confined source of energy such as a focused laser beam. Here we combine laser excitation with X-ray magnetic imaging to determine the effect of laser heating on the local and transient magnetization of FeRh using time-resolved photoelectron emission microscopy. Excitation by an ultrashort laser pulse generates a local ferromagnetic state within 0.6ns which recovers its initial antiferromagnetic state after a further 2ns. The form of the domains during the growth and diminution of ferromagnetic ordering suggests an intrinsic speed limit for magnetic and structural changes.

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