Plasma sputtering system upgrade

We are pleased with the completion of the first part of our LabLine Plasma Sputtering upgrade. The system has been improved by adding a second mass flow controller (MFC) to allow the Oxygen / Argonne reactive plasma sputtering of oxide dielectric materials. The second part of the upgrade is to connect the Oxygen gas bottle to the MFC.
The ECLIPSE software has been already upgraded. This is an excellent capability / addition that will support at least two L6 project students this year and one PhD student research.

Our first research paper on KJL LabLine Plasma Sputtering system published

 Physica B: Condensed Matter, Volume 525, 15 November 2017, Pages 12-15

Development of flexible Ni₈₀Fe₂₀ magnetic nano-thin films 

 M.M. Vopson, J. Naylor, T. Saengow, E.G. Rogers, S. Lepadatu, Y.K. Fetisov

Flexible magnetic Ni₈₀Fe₂₀ thin films with excellent adhesion, mechanical and magnetic properties have been fabricated using magnetron plasma deposition. We demonstrate that flexible Ni₈₀Fe₂₀ thin films maintain their non-flexible magnetic properties when the films are over 60 nm thick. However, when their thickness is reduced, the flexible thin films display significant increase in their magnetic coercive field compared to identical films coated on a solid Silicon substrate. For a 15 nm flexible Ni₈₀Fe₂₀ film coated onto 110 µm Polyvinylidene fluoride polymer substrate, we achieved a remarkable 355% increase in the magnetic coercive field relative to the same film deposited onto a Si substrate. Experimental evidence, backed by micro-magnetic modelling, indicates that the increase in the coercive fields is related to the larger roughness texture of the flexible substrates. This effect essentially transforms soft Ni₈₀Fe₂₀ permalloy thin films into medium/hard magnetic films allowing not only mechanical flexibility of the structure, but also fine tuning of their magnetic properties.

Get full text here: https://authors.elsevier.com/a/1VgqF3HWvdxey4

A big welcome to our new PhD students in AML

Two new PhD students have been recruited to work in the Applied Materials Laboratory under Dr Vopson's supervision. Mr Michal Belusky will undertake a full time research project investigating "Deposition of flexible thin films via magnetron plasma sputtering". Mr Andrew Nomuoja will start his part-time PhD on a project involving theoretical and experimental studies of polarization dynamics in ferroelectric and anti-ferroelectric materials. We wish a warm welcome to both new members and best of luck with their research projects.

A memory effect in anti-ferroelectric materials discovered

Initial studies of anti-ferroelectric materials in the Applied Materials Laboratory at the University of Portsmouth indicate that these polar dielectrics can store digital information. The experimental results are very encouraging and an article is in preparation. Dr Vopson and Prof. Tan from Iowa State University, are currently working on the proposal of a novel anti-ferroelectric random access memory chip (AFRAM) that will compete with traditional ferroelectric random access memory (FRAM) to deliver twice the memory storage capacity in the same volume.

New Research published on Multicaloric Effect

The induced magnetic and electric fields’ paradox leading to multicaloric effects in multiferroics

M.M. Vopson 

Solid StateCommunications231-232(2016)14–16 

A b s t r a c t

Magneto-electric effect in multiferroics implies that an applied magnetic field induces an electric polarization change in a multiferroic solid and viceversa, an applied electric field modifies its magnetization. The magneto-electric effect is a powerful feature of multiferroics and has attracted huge interest due to potential technological applications.One such possible application is the multicaloric effect in multiferroics. However, a closer examination of this effect and its derivation leads to a paradox, in which the predicted changes in one of the order phase at a constant applied field are due to the excitation by the same field. Here this apparent paradox is first explained in detail and then solved. Understanding how electric and magnetic fields can be induced in multiferroic materials is an essential tool enabling their theoretical modeling as well as facilitating the introduction of future applications.
& 2016Elsevier Ltd. All rights reserved.

Full text: http://dx.doi.org/10.1016/j.ssc.2016.01.021

Applied Materials nano-Thin Films Laboratory becomes fully functional

The nano-thin films teaching laboratory within the Applied Materials Laboratory at the University of Portsmouth becomes fully operational. This is a major teaching facility that will deliver at least 2-3 student projects per year, as well as PhD and MSc/Mres research work.


Thin films deposition via plasma magnetron sputtering



LabLine Kurt J. Lesker Plasma Sputtering System
5 magnetron targets, 4 DC and one RF
One magnetron target for magnetic materials
4 substrates holder with automated indexing for
deposition of individual or multi-layers
Substrates heater up to 450 C
2 Quartz thickness rate monitors (resolution 0.1 A/s)

Applications of multiferroic materials review published

Fundamentals of Multiferroic Materials and Their Possible Applications
Melvin M. Vopson (2015): Fundamentals of Multiferroic Materials and Their Possible Applications, Critical
Reviews in Solid State and Materials Sciences, DOI: 10.1080/10408436.2014.992584

This article is the basis of the Introduction to Multiferroic materials and their Application teaching Unit offered by Dr Vopson to University of Portsmouth Applied Physics students at Level 6 / year 3. Most of the teaching material is now published in this major review article.  

Abstract
Materials science is recognized as one of the main factors driving development and economic growth. Since the silicon industrial revolution of the 1950s, research and developments in materials and solid state science have radically impacted and transformed our society by enabling the emergence of the computer technologies, wireless communications, Internet, digital data storage, and widespread consumer electronics. Today’s emergent topics in solid state physics, such as nano-materials, graphene and carbon nano-tubes, smart and advanced functional materials, spintronic materials, bio-materials, and multiferroic materials, promise to deliver a new wave of technological advances and economic impact, comparable to the silicon industrial revolution of the 1950s. The surge of interest in multiferroic materials over the past 15 years has been driven by their fascinating physical properties and huge potential for technological applications. This article addresses some of the undamental aspects of solid-state multiferroic materials, followed by the detailed presentation of the latest and most interesting proposed applications of these multifunctional solid-state compounds. The applications presented here are critically discussed in the context of the state-of-the-art and current scientific challenges. They are highly interdisciplinary covering a wide range of topics and technologies including sensors, microwave devices, energy harvesting, photo-voltaic technologies, solid-state refrigeration, data storage recording technologies, and random access multi-state memories. According to their potential and expected impact, it is estimated that multiferroic technologies could soon reach multibillion US dollar market value.
To link to this article: http://dx.doi.org/10.1080/10408436.2014.992584

Novel magnetic data storage beyond super-paramagnetic limit

Multiferroic composites for magnetic data storage beyond the super-paramagnetic limit

Researchers in the Applied Materials Laboratory at the University of Portsmouth led by Dr Vopson, in collaboration with colleagues from Institute Jozef Stefan - Slovenia, published a novel concept of multiferroic magnetic data storage that functions beyond the super-paramagnetic limit. 
JOURNAL OF APPLIED PHYSICS 116, 113910 (2014)

Abstract
Ultra high-density magnetic data storage requires magnetic grains of <5 nm diameters. Thermal stability of such small magnetic grain demands materials with very large magneto-crystalline anisotropy, which makes data write process almost impossible, even when Heat Assisted Magnetic Recording (HAMR) technology is deployed. Here, we propose an alternative method of strengthening the thermal stability of the magnetic grains via elasto-mechanical coupling between the magnetic data storage layer and a piezo-ferroelectric substrate. Using Stoner-Wohlfarth single domain model, we show that the correct tuning of this coupling can increase the effective magnetocrystalline anisotropy of the magnetic grains making them stable beyond the super-paramagnetic limit. However, the effective magnetic anisotropy can also be lowered or even switched off during the write process by simply altering the applied voltage to the substrate. Based on these effects, we propose two magnetic data storage protocols, one of which could potentially replace HAMR technology,
with both schemes promising unprecedented increases in the data storage areal density beyond the super-paramagnetic size limit. VC 2014 AIP Publishing LLC.

[http://dx.doi.org/10.1063/1.4896129]

Applied Materials Laboratory (AML) Blog launch

The lead scientist of the Applied Materials Laboratory (AML) at the University of Portsmouth has officially launched the AML Blog on the 19^th of March 2014. 

The Blog will offer regular updates on the core teaching and research activities within this laboratory. 

We welcome contributors and comments, especially from our students. To get access as contributor please contact Dr Vopson.