Magnetic resonance and ferromagnetic behaviour in Fe-implanted SrTiO3

doi:10.1016/j.ssc.2009.10.041

Solid State Communications

Volume 150, Issues 3–4, January 2010, Pages 219-222

https://doi.org/10.1016/j.ssc.2009.10.041 Get rights and content

Abstract

The results of magnetic resonance and magnetization measurements of Fe-implanted strontium titanate (SrTiO₃) are presented. Electron paramagnetic resonance (EPR) spectra including resonance lines due to the paramagnetic Fe³⁺–V _o site with axially disturbed ligand field, and due to $S$ -state Fe³⁺ ions ( $S = 5 / 2$ and $L = 0$ ) substituted into the titanium site coordinated by six oxygen atoms in the Ti⁴⁺-centered unit cell, were observed. It has been revealed that the implantation of Fe ions into SrTiO₃ produces a remarkable ferromagnetic behavior. The ferromagnetic resonance (FMR) and magnetization measurements revealed an out-of-plane uniaxial magnetic anisotropy in Fe-implanted SrTiO₃. The observed phenomena are discussed on the basis of strong magnetic dipolar interaction between Fe nanoparticles due to the decreasing interparticle distance with increasing implantation fluence.

Introduction

Investigations of the magnetic and electrical properties of composite systems representing dispersed magnetic nanoparticles embedded in a dielectric host are of great interest due to the wide range of potential applications of these materials in the fields of magnetoelectronics and spintronics, including magnetic recording, magnetosensor electronics, magnetooptical devices, etc. [1]. On the other hand, these structures provide a good model system for studying experimentally fundamental phenomena in nanomagnetism [2], [3]. Particularly interesting phenomena occur when the nanoparticles are coupled by magnetic interactions [4], [5], [6], [7]. In particular, the ability to tune magnetic interactions in nanoparticle systems is of great importance [8].

The magnetic properties of such composites can be controlled on a large scale by varying the average nanoparticle size, distribution, packing factor, and composition of the magnetic inclusions and surrounding diamagnetic medium. Actually there are a number of different techniques for obtaining composite materials with controlled structural and magnetic characteristics. Among these techniques, ion implantation is a very attractive and prospective preparation method, which has a number of advantages: easy control of the metal distribution and concentration; the availability of almost arbitrary metal–dielectric compositions; and the ability to surpass the solubility limits constrained by the chemical and thermodynamic equilibrium of the host matrix and metal impurities [9]. Besides, the ion implantation technique is ideally suited for the fabrication of thin-film magnetic media and planar devices for magnetosensor electronics.

In this paper the results of investigations of magnetic resonance spectra and magnetization measurements of Fe-implanted perovskite SrTiO₃ crystals are presented. These results show the promise of ferroelectric perovskite for potential magnetoelectric applications and the flexibility of ion implantation as a method for introducing of transition metal impurities into host materials for purposes of measuring their magnetic properties using different experimental techniques.

Section snippets

Experimental

The samples were prepared by Fe ion implantation into (100)-oriented single-crystalline plates of SrTiO₃ substrates with 40 kEv iron ions at fluences between 0.5×10¹⁷ and 1.5×10¹⁷ ion/cm² and with a current density of 8 μA/cm².

Magnetic resonance measurements were carried out using a Bruker EMX model X-band (9.8 GHz) spectrometer. The spectra were recorded at room temperature and for various orientations of the implanted surface with respect to the applied DC magnetic field ( $H$ ) by varying the

Results and discussion

The results of magnetic resonance measurements of Fe-implanted SrTiO₃ performed in the “in-plane” and “out-of-plane” geometries are presented in Fig. 1. As is seen from the figure, the magnetic resonance spectra exhibit both EPR and FMR peaks, which can be interpreted as evidence of the formation of both Fe centers inside the crystal structure and ferromagnetic Fe nanoparticles. The rotational EPR patterns for the “in-plane” and “out-of-plane” geometries are presented in Fig. 2. As is seen from

Conclusion

In conclusion, the results of magnetic resonance investigations of Fe-implanted strontium titanate (SrTiO₃) perovskite crystals revealed both the presence of anisotropic EPR spectra and remarkable ferromagnetic behaviour. The EPR spectra showed the presence of two different Fe centers in the SrTiO₃ crystal structure with characteristic cubic and axially distorted surroundings. It has been revealed that the implantation of Fe into SrTiO₃ with different fluences of metal concentrations produces a

Acknowledgements

The authors acknowledge Dr. Bulat Rameev for his fruitful discussion. FAM is indebted to the Research Projects Commission of Gebze Institute of Technology for supporting this work with Grant No. 2009-A-11. The authors from Kazan Physical-Technical Institute, Russia, acknowledge support through the RFFI, grant 07-02-00559, OFN RAN Programme “New material and structures”, and Russian Federal Agency on Education, contract P902.

References (21)

J.F. Löffler et al.
Phys. Rev. Lett.
(2000)
R.V. Chamberlin et al.
Phys. Rev. B
(2002)
R.P. Cowburn et al.
Science
(2000)
W. Kleemann et al.
Phys. Rev. B
(2001)
S.T. Chui et al.
Phys. Rev. B
(2002)
P.J. Jensen et al.
Phys. Rev. B
(2003)
V.F. Puntes et al.
Nat. Mater.
(2004)
G. Dearnaley et al.
Ion Implantation
(1973)
R.A. Serway et al.
Phys. Rev. B
(1977)

There are more references available in the full text version of this article.

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Magnetic resonance and ferromagnetic behaviour in Fe-implanted SrTiO3

Abstract

Introduction

Section snippets

Experimental

Results and discussion

Conclusion

Acknowledgements

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