Enhancement of magnetic properties in compressively strained PrVO3 thin films

Abstract

Strain engineering is an important issue in oxides thin lms to explore new functionalities. Here, a series of high quality epitaxial PrVO 3 (PVO) thin lms were grown, by Pulsed Laser Deposition (PLD) technique, as a function of thickness on (La,Sr)(Al,Ta)O 3 (100) [LSAT (100)] and LaAlO 3 (100) [LAO (100)] substrates with nominal lattice mismatch of-0.8 % and-2.9 %, respectively. The X-ray diraction revealed a constant out-of-plane lattice parameter of PVO/LSAT with increase in lm thickness, while a rather continuous decrease for PVO/LAO lms. Whereas thicker PVO lms show a ferromagnetic-like behavior, at low thickness a surprising decrease of coercivity (H c) and increase of saturation magnetization (M s) is observed. This behavior is described using a classical model of dead layer which possesses a strong paramagnetic susceptibility. It is also shown how capping of PVO lm can aid in recovering the pure magnetic properties of PVO, by diminishing the contribution from dead layer. Finally, the Néel temperature (T N) is examined as a function of lm thickness, and found to vary in the range of 25 K and 30 K for LSAT and LAO, respectively. These results pave the way for the use of vanadate in thin lm devices.

Strong Magnetic Anisotropy of Epitaxial PrVO3 Thin Films on SrTiO3 Substrates with Different Orientations

“…In fact, we have recently shown that a dead layer of ∼ 5 nm in thickness, which is composed of mainly V 4+ ions, is responsible for the increase of magnetization for low thicknesses lms [10].…”

“…In fact, we have recently shown that a dead layer of ∼5 nm in thickness exists at the surface of the film, which is mainly composed of V 4+ /V 5+ ions. 11 The V 4+ /V 5+ ions can decouple the Pr 3+ ions, leading Pr atoms to unleash their strong paramagnetic response and could partially explain the increase of magnetization for low thickness films. The dead layer was also invoked to explain the small magnetic component (i.e., soft magnetic component) at low fields (∼0.2 T).…”

“…The first contribution from the dead layer was earlier seen to be partially responsible for the observed steps in the hysteresis loop. 11 The second contribution could be related to the magnetic domains which seems to be similar to the bulk behavior with a very small coercivity. 2 The magnetic anisotropy of the PVO films was characterized by M−H curves after the subtraction of the diamagnetic contribution from the oriented STO substrates (see ref 27 for substrates magnetism).…”

“…Through X-ray Photoelectron Spectroscopy (XPS), the formation of an over-oxidized dead-layer (45 nm) on the surface of PVO lm was earlier revealed, consisting of isolated Pr atom. Furthermore, this dead-layer has a large paramagnetic contribution, whose impact gradually diminishes with the increase of lm thickness [10]. The over-oxidation of the lm surface is quite common in vanadium oxide thin lms, which tends to oxidize during growth process [11,12].…”

Epitaxial growth and structure of LaVO3 and PrVO3 thin films

“…So far, RVO 3 films have been grown by pulsed laser deposition (PLD) [24] or by MBE [25]. While the effect of strain on the VO 6 octahedra rotations [26,27] or La motions have also been investigated in LVO thin films grown by PLD [28], tunable magnetic properties has been observed in PVO thin films either as a function of the epitaxial strain [29,30] or the chemical strain through the control of oxygen vacancy concentration [31,32].…”