Folkers, Bart

Hilgenkamp, Hans

Jansen, Thies

Marques do Rosário, Carlos Miguel

Roskamp, Thijs Jasper

English

University of Twente Research Information

Suppression of ferromagnetism using Ti layers Oxygen scavenging by the Ti layerPatterning ferromagnetism in LaMnO3Controlling ferromagnetism in LaMnO3/SrTiO3 thin films using Ti oxygen scavenging layersThijs Roskamp1,*, Thies Jansen1, Bart Folkers1, Carlos Rosário1,2 and Hans Hilgenkamp1;1MESA+ Institute of Technology, University of Twente, 7500AE Enschede, The Netherlands;2International Iberian Nanotechnology Laboratory, 4715-330 Braga, Portugal;*E-mail: t.j.roskamp@utwente.nlIntroductionReferences[1] Wang et al. Science 349: 716 (2015)[2] Ahn et al. Physical Review B 64(11): 115103 (2001)[3] Hemberger et al. Physical Review B 66(9): 094410 (2002)o Ti layers suppress ferromagnetism in LaMnO3o Ti oxygen scavenging can influence the FM to AFM transitiono FM can be structured down to nanoscale dipole-like magnets  o TEM investigation of the Ti/LMO interfaceo Interactions between LMO nanomagnetso Mechanisms for ferromagnetism in LMOConclusions and Future Worko SQUID measures noise for LMO/STO covered by Ti/Auo Ti layer influences FM of LMOo Au is capping layero Patterning FM structures in LMO persists till nanoscaleo Decrease in FM dependent on: o Reactive metals like Ti are oxygen scavenging, creating oxygen vacancies at LMO/Ti interfaceScanningSQUID Microscopyo High sensitivity due to flux-locked loop and modulation coilo Scanning SQUID Microscopy (SSM) probes magnetic flux from a surface using a DC SQUIDVΦmax dV/dΦΦ0VΦIbSuperconducting QUantum Interference Device (SQUID)o Magnetic signal is picked up remotely using a pickup loopOur SSM:Spatial resolution ~ 5-10 𝛍𝐦Field resolution ~ 10 𝐧𝐓DC SQUID washer≈ 9 μmPickup loopSQUID Signal [μT]6-6 30-3o Uncovered LMO/STO has clear FM signalo SSM pickup loop (15-20 μm2) convolutes FM domains by averagingo True LaMnO3ferromagnetic domains are smallerSQUID Signal [μT]20-20 100-10d=30 μmd=10 μmd=20 μm3-3 0SQUID Signal [μT]2510-10 0SQUID Signal [μT]5 μm 2.550 μmo Asymmetric structures show multiple domainso Decreasing distance between micromagnets leads to interactionso Shape restraintsforce ‘dipole’ signals toorient along the structures long-axisSQUID Signal [μT]05-52.5Ti/AuLMO21 μm250 nm100 nm500 nm1.5o Small structureshave smaller SQUID signalso Below ~ 5 μmsignal is like in-plane magnetic dipoleSingle domain LMO?dLMO5x5μmTi/AuLMO25201510 μm 5 12.5o XRD indicatesi. Timeii. Ti and LMO layer thicknesschange in lattice parameter due to shift of LMO (002) reflectiono Oxygen vacancies can:i. Change the valence of Mn ionsii. Cause strain relaxationLaMnO3 (LMO)Antiferromagnetism (AFM)Ferromagnetism (FM)Strain [2]Thickness [1]Doping [3]Valence of Mn ionsOrbital ordering Electron exchange processesIndirect exchange via oxygen ionsAFM superexchangeFM superexchangeFM double exchange50 uc LMO24 nm TiSTO (002)LMO (002)Shape restraints and interactions

Controlling ferromagnetism in LaMnO3/SrTiO3 thin films using Ti oxygen scavenging layers

https://ris.utwente.nl/ws/files/305607509/NEMPoster_MagnetismLMO_FinishedV2_1.pdf

Controlling ferromagnetism in LaMnO3/SrTiO3 thin films using Ti oxygen scavenging layers

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