Iron-Doped Lithium Tantalate Thin Films Deposited by Magnetron Sputtering: A Study of the Iron Role in the Structure and the Derived Magnetic Properties

Sergio David Villalobos Mendoza,José Rurik Farías Mancilla,José Trinidad Holguín Momaca,José Trinidad Elizalde Galindo,Diana María Carrillo Flores,Sion Federico Olive Méndez

doi:10.3390/cryst10010050

Sergio David Villalobos Mendoza, José Rurik Farías Mancilla + Show 4 more

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https://doi.org/10.3390/cryst10010050

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Abstract

Fe-doped LiTaO3 thin films with a low and high Fe concentration (labeled as LTO:Fe-LC and LTO:Fe-HC, respectively) were deposited by magnetron sputtering from two home-made targets. The dopant directly influenced the crystalline structure of the LiTaO3 thin films, causing the contraction of the unit cell, which was related to the incorporation of Fe3+ ions into the LiTaO3 structure, which occupied Li positions. This substitution was corroborated by Raman spectroscopy, where the bands associated with Li-O bonds broadened in the spectra of the samples. Magnetic hysteresis loops, zero-field cooling curves, and field cooling curves were obtained in a vibrating sample magnetometer. The LTO:Fe-HC sample demonstrates superparamagnetic behavior with a blocking temperature of 100 K, mainly associated with the appearance of Fe clusters in the thin film. On the other hand, a room temperature ferromagnetic behavior was found in the LTO:Fe-LC layer where saturation magnetization (3.80 kAm−1) and magnetic coercivities were not temperature-dependent. Moreover, the crystallinity and morphology of the samples were evaluated by X-ray diffraction and scanning electron microscopy, respectively.

Highlights

ABO3 -type oxides represent an important group of materials in the classification of advanced ceramics since a large variety of physical properties can be ascribed to them, such as ferroelectricity, piezoelectricity, electrostriction, and pyroelectricity [1]
When a structural analysis was performed on lithium tantalate nanoparticles, a 0.5 wt.% Fe-doped lithium tantalate target (T1), and a 1.8 wt.% Fe-doped lithium tantalate target (T2), the computed volumes of the unit cells were similar, which indicated that the Fe did not substitute completely into the crystalline structure of targets
Bonds of the crystalline structure of T1 and T2 were affected during the sintering process due to the generation of lithium vacancies, which was reflected by the broadening of Raman peaks associated to the Li–O bonds

Summary

Introduction

ABO3 -type oxides represent an important group of materials in the classification of advanced ceramics since a large variety of physical properties can be ascribed to them, such as ferroelectricity, piezoelectricity, electrostriction, and pyroelectricity [1]. It is common to modify the physical properties of ABO3 -type materials by the addition of different kinds of dopants at the A or B sites. Concerning their magnetic properties, it is well known that ferromagnetism can be induced in these types of materials by doping with elements containing d, f, and sp electrons, as well as promoting cation and anion vacancies. LT has been synthesized in the form of particles [8,9,10], Crystals 2020, 10, 50; doi:10.3390/cryst10010050 www.mdpi.com/journal/crystals

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