A Strategy for Enhancing Perpendicular Magnetic Anisotropy in Yttrium Iron Garnet Films

In future information storage and processing, magnonics is one of the most promising candidates to replace traditional microelectronics. Yttrium iron garnet (YIG) films with perpendicular magnetic anisotropy (PMA) have aroused widespread interest in magnonics. Obtaining strong PMA in a thick YIG film with a small lattice mismatch (η) has been fascinating but challenging. Here, a novel strategy is proposed to reduce the required minimum strain value for producing PMA and increase the maximum thickness for maintaining PMA in YIG films by slight oxygen deficiency. Strong PMA is achieved in the YIG film with an η of only 0.4% and a film thickness up to 60 nm, representing the strongest PMA for such a small η reported so far. Combining transmission electron microscopy analyses, magnetic measurements, and a theoretical model, it is demonstrated that the enhancement of PMA physically originates from the reduction of saturation magnetization and the increase of magnetostriction coefficient induced by oxygen deficiency. The Gilbert damping values of the 60-nm-thick YIG films with PMA are on the order of 10-4 . This strategy improves the flexibility for the practical applications of YIG-based magnonic devices and provides promising insights for the theoretical understanding and the experimental enhancement of PMA in garnet films.

Electric and Magnetic Tuning of Gilbert Damping Constant in LSMO/PMN-PT(011) Heterostructure

Electric field control of magnetodynamics in magnetoelectric (ME) heterostructures has
been the subject of recent interest due to its fundamental complexity and promising applications in
room temperature devices. The present work focuses on the tuning of magnetodynamic parameters
of epitaxially grown ferromagnetic (FM) La_0.7Sr_0.3MnO₃(LSMO) on a ferro(piezo)electric (FE)
Pb(Mg_0.33Nb_0.67)O₃-PbTiO₃(PMN-PT) single crystal substrate. The uniaxial magnetic anisotropy
of LSMO on PMN-PT confirms the ME coupling at the FM/FE heterointerface. The magnitude of
the Gilbert damping constant (α) of this uniaxial LSMO film measured along the hard magnetic axis
is significantly small compared to the easy axis. Furthermore, a marked decrease in the α values of
LSMO at positive and negative electrical remanence of PMN-PT is observed, which is interpreted
in the framework of strain induced spin dependent electronic structure. The present results clearly
encourage the prospects of electric field controlled magnetodynamics, thereby realising the room
temperature spin-wave based device applications with ultra-low power consumption.