Structure and Properties of Nanomaterials from ab initio Studies
Department of Physics, Colorado State University, Fort Collins, CO 80523, USA
Materials on a nanometer scale exhibit unique atomic, electronic, optical and magnetic properties.
Understanding the interplay between structure and properties of these nanomaterials is critical for
their applications as sensors, nano-devices and coatings.
Magnetic nanostructures and multilayers are widely used in computer hard drives. Fe/W(110) and
Fe/Mo(110) ultrathin films are ideal systems to understand the interplay between structure and
magnetism due to their thermostability, pseudomorphic layer-by-layer growth, and potential application
as perpendicular magnetic recording media.
We have investigated the atomic structure, magnetic moment and magnetocrystalline anisotropy
of Fe/W(110) ultrathin films employing the highly accurate full-potential linearized augmented plane-wave
(FP-LAPW) method. The surface and interfacial layers exhibit strong relaxations.
Significant enhancement of the surface magnetic moment and large interface Fe/W anisotropy were found.
Surprisingly, Hund¡¯s third rule was found to be violated for W atoms confirmed by recent experimental observations.
It has been demonstrated that surface stress plays an important role in surface diffusion, reconstruction,
morphology, and magnetic domains. Surface stress also affects nano-device applications due to
the large surface to volume ratio in nanomaterials. However, surface stress is very difficult to
measure and quantify. To date, it has not been possible to measure surface stress on a bare substrate directly.
We have developed a composite elastic model and applied this model to calculate theoretically
the surface stress of 7 monolayer (ML) Mo(001) thin films. Relaxation was found to reduce
surface stress by as much as 40%.