Berlin 2005 – scientific programme

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MA: Magnetismus

MA 15: Magnetische Kopplungsph
änomene / Exchange Bias

MA 15.10: Talk

Saturday, March 5, 2005, 16:15–16:30, TU H1028

Detection of Spin and Charge States in Centrosymmetric Materials by Nonlinear Optics — •T. Satoh^1,2, Th. Lottermoser¹, M. Fiebig¹, Y. Ogimoto^2,3, H. Tamaru², M. Izumi², K. Miyano², and S. Ishihara⁴ — ¹Max-Born-Institut, Max-Born-Straße 2A, 12489 Berlin — ²RCAST, University of Tokyo, Meguro-ku, Tokyo 153-8904, Japan — ³Devices Technology Res. Labs., SHARP Corp., Nara, Japan — ⁴Dept. of Physics, Tohoku University, Sendai 980-8578, Japan

Over the last decade nonlinear optics has evolved into a powerful tool for studying the magnetic properties of matter. We investigated two magnetic systems with multiphoton techniques where linear optical methods fail. (i) The interface of transition metal oxides has attracted recent attention: it represents a 2D electron system in titanates and displays interface ferromagnetism in manganites. Degradation of tunnelling magnetoresistance due to charge transfer at the interface has been suggested. We apply interface sensitive second harmonic generation to manganite thin films and reveal the nature of charge transfer at the interface. The experimental results were compared with theoretical calculations. (ii) Resonance-enhanced sum-frequency generation is introduced as novel tool for investigation of magnetically ordered compounds. A tunable laser at frequency ω₁ is used to excite an intermediate electronic transition resonantly while a second laser at frequency ω₂ is used to scan the nonlinear spectrum at ω₁+ω₂. The technique is particularly useful for the investigation of centrosymmetric structures that the majority of magnetic compounds possess. The technique is demonstrated on antiferromagnetic NiO.