• PDF / 568,633 Bytes
• 9 Pages / 584.957 x 782.986 pts Page_size
• 88 Downloads / 242 Views

DOWNLOAD

REPORT

---

Wei Lua) Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, People’s Republic of China

Hai Wang College of Materials Science and Engineering, Tongji University, Shanghai 201804, People’s Republic of China

Haitao Huang and Jiyan Dai Department of Applied Physics, The Hong Kong Polytechnic University, Hong Kong, People’s Republic of China (Received 5 January 2012; accepted 21 March 2012)

The ground-state structural, electronic, magnetic, optical and dielectric properties of MnTiO3 are calculated using density functional theory within the generalized gradient approximation. The structure parameters obtained agree well with experimental results. The electronic structure results show that the G-type antiferromagnetic phase of LN-type MnTiO3 has an indirect band gap of 0.85 eV. The calculated local magnetic moment of Mn ion is 4.19 lB. The calculated Born effective charges (BECs, denoted by tensor Z*) show that the Z* of Ti and O atoms are significantly and anomalously large. Interestingly, ferroelectric spontaneous polarization of large magnitude is predicted to be along [111] direction with a magnitude of 87.95–105.22 lC/cm2. B-site Ti ions in 3 d 0 state dominate ferroelectric polarization of multiferroic MnTiO3, whereas A-site Mn ions having partially filled 3 d5 orbitals are considered to contribute to its antiferromagnetic properties. Furthermore, it is predicted that multiferroic MnTiO3 shows good dielectric and optical properties.

I. INTRODUCTION

Perovskite-type (ABO3) multiferroic materials have received considerable attention in recent years; the multiferroics have coupled magnetic, electric, and/or electronic structural order parameters that result in both (anti) ferromagnetism, ferroelectricity, and/or ferroelasticity in the same phase.1–3 With this coexistence, they have the spontaneous magnetization that can be switched on by an applied magnetic field, also the spontaneous polarization that can be tuned by an electric field. Owing to the coupling between magnetic and ferroelectric orders, this can lead to magnetoeletric effect, in which magnetization can be switched on by an applied electric field and vice versa.2–5 The mutual control of electric and magnetic properties is of significant interest for applications in memory storage devices, electric field-controlled ferromagnetic resonance devices, sensors, actuators and other potential devices.6–9 Besides the application aspects of this technology, the fundamental physics of magnetoelectric coupling is also important for understanding the intrinsic physical properties. Many efforts have been a)

Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2012.101 J. Mater. Res., Vol. 27, No. 11, Jun 14, 2012

devoted to theoretically investigate multiferroic materials over the last decade.9–15 It is recognized that ferroelectricity and ferromagnetism are rarely found in the same system because the conventional off-center distortion of the B ion in d0 state responsible for polar behavior is usually i