| 1. |
- Araujo, Carlos Moyses, et al.
(författare)
-
Disorder-induced Room Temperature Ferromagnetism in Glassy Chromites
- 2014
-
Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 4, s. 4686-
-
Tidskriftsartikel (refereegranskat)abstract
- We report an unusual robust ferromagnetic order above room temperature upon amorphization of perovskite [YCrO3] in pulsed laser deposited thin films. This is contrary to the usual expected formation of a spin glass magnetic state in the resulting disordered structure. To understand the underlying physics of this phenomenon, we combine advanced spectroscopic techniques and first-principles calculations. We find that the observed order-disorder transformation is accompanied by an insulator-metal transition arising from a wide distribution of Cr-O-Cr bond angles and the consequent metallization through free carriers. Similar results also found in YbCrO3-films suggest that the observed phenomenon is more general and should, in principle, apply to a wider range of oxide systems. The ability to tailor ferromagnetic order above room temperature in oxide materials opens up many possibilities for novel technological applications of this counter intuitive effect.
|
|
| 2. |
- Araujo, C. Moysés, et al.
(författare)
-
Room temperature ferromagnetism in pristine MgO thin films
- 2010
-
Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 96:23
-
Tidskriftsartikel (refereegranskat)abstract
- Robust ferromagnetic ordering at, and well above room temperature is observed in pure transparent MgO thin films (<170 nm thick) deposited by three different techniques. Careful study of the wide scan x-ray photoelectron spectroscopy rule out the possible presence of any magnetic contaminants. In the magnetron sputtered films, we observe magnetic phase transitions as a function of film thickness. The maximum saturation magnetization of 5.7 emu/cm(3) is measured on a 170 nm thick film. The films above 500 nm are found to be diamagnetic. Ab initio calculations suggest that the ferromagnetism is mediated by cation vacancies.
|
|
| 3. |
- Biswas, Anis, et al.
(författare)
-
The effect of oxygen partial pressure during deposition in the magnetic properties of ZnO thin film
- 2011
-
Ingår i: Mater Res Soc Symp Proc. - : Springer Science and Business Media LLC. - 9781605112695 ; , s. 117-122
-
Konferensbidrag (refereegranskat)abstract
- We have studied the magnetic properties of 100 nm thick ZnO thin films prepared by magnetron sputtering in different oxygen partial pressures (ratio of oxygen pressure to total pressure in deposition chamber, P Oxy). Only the films fabricated at P Oxy below ∼ 0.5 show room temperature ferromagnetism. The saturation magnetization at room temperature is initially found to increase as P Oxy increases and reaches maximum value of ∼ 5 emu/gm at P Oxy ∼ 0.3 and then starts to decrease and becomes diamagnetic for P Oxy > 0.5. From small angle XRD study of structural properties of the films, we find that the lattice stress developed in the film along c-axis also exhibits a similar behavior with the variation of P Oxy. Thus, both the room temperature ferromagnetism and lattice stress appear to originate from the intrinsic defects present in the sample.
|
|
| 4. |
- Chawla, Amit Kumar, et al.
(författare)
-
Study of composition dependent structural, optical, and magnetic properties of Cu-doped Zn1-xCdxS nanoparticles
- 2010
-
Ingår i: Journal of Applied Physics. - : AIP Publishing. - 0021-8979 .- 1089-7550. ; 108:12, s. 123519-
-
Tidskriftsartikel (refereegranskat)abstract
- Cu-doped Zn1-xCdxS nanoparticles were synthesized by coprecipitation technique in ice bath at 280 K. The band gap energy of Zn1-xCdxS:Cu nanoparticles can be tuned to a lower energy by increasing the Cd content, indicating the formation of the alloyed nanoparticles. The alloy structure is further supported by the systematic shifting of characteristic x-ray diffraction peaks to lower angles with increase in Cd content. Systematic copper doping induces a red shift in the energy band gap of Zn0.9Cd0.1S:Cu nanoparticles with increase in copper concentration. Cu-doped Zn0.9Cd0.1S nanoparticles were found to have ferromagnetic nature at 5 K whereas undoped particles were found to be diamagnetic. Green luminescence further proves proper doping of Cu into the ZnCdS matrix. It is believed that the green luminescence originates from the recombination between the shallow donor level (sulfur vacancy) and the t(2) level of Cu2+. This method provides an inexpensive and simple procedure to produce ternary ZnCdS: Cu nanoparticles with tunable optical properties via changing Cd and/or Cu concentrations.
|
|
| 5. |
- Kaushik, Neelam, et al.
(författare)
-
Exchange-coupled FePtB nano-composite hard magnets produced by pulsed laser deposition
- 2010
-
Ingår i: Materials Science & Engineering. - : Elsevier BV. - 0921-5107 .- 1873-4944. ; 171:1-3, s. 62-68
-
Tidskriftsartikel (refereegranskat)abstract
- Nano-composite FePtB thin films were deposited on naturally oxidized (1 0 0) silicon (Si) and glass (SiO2) substrates by using a pulsed laser deposition (PLO) technique. Effects of processing conditions on structural, surface and magnetic properties of the films were examined. Growth temperature (T-s) and the type of substrate (Si or SiO2) are shown to affect crystal structure and magnetic properties of FePtB thin films significantly. Under optimized processing conditions, a similar to 1.7 mu m thick FePtB film deposited on a glass substrate exhibits high coercivity (similar to 7.7 kOe), high reduced remanence [(M-r/M-s) similar to 0.9] and high energy product (BH)(max) = 71 kJ/m(3). The films exhibiting good hard magnetic properties are mainly made-up of nano-sized hard (L1(0)-FePt) and soft (iron-boride) magnetic phases, which are shown to be exchange coupled. Fabrication of hard magnetic thin films by a simple and fast technique such as PLD is very promising for the production of micro magnets for MEMS applications.
|
|
| 6. |
|
|
| 7. |
- Moysés Araújo, C., et al.
(författare)
-
Transformation to Room Temperature Ferromagnetism on Amorphizing Chromite Thin Films
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Transformation to Ferromagnetic order above room temperature is observed on amorphizing otherwise antiferromagnetic chromite [Y(Yb)CrO3] thin films produced by pulsed laser deposition.. To understand the underlying physics of this phenomenon, we have combined advanced spectroscopy techniques and first-principles calculations. The amorphization is found to be accompanied by an insulator-metal transition, which in turn affects the magnetic properties. The ferromagnetism (FM) is then explained by evoking a number of coexisting effects, namely disordering of Cr-O-Cr bond angles, metallization which introduces free carriers and the presence of mixed valence states (Cr3+ in the bulk and Cr4+ on the surface). They favor FM coupling through double and direct exchange interactions. Although we have used YCrO3 as case study, our results are more general and must apply for a wide range of oxide systems.
|
|
| 8. |
|
|
| 9. |
- Nagar, Sandeep, et al.
(författare)
-
A new material for Magneto-Optical applications : (Fe72B24Nb4)95.5Y4.5 glassy thin film
-
Tidskriftsartikel (övrigt vetenskapligt/konstnärligt)abstract
- Magneto-Optical properties have been investigated for new kind of glassy thin films. 5, 8, 25 and 30 nm (Fe72B24Nb4)95.5Y4.5 thin films were fabricated using Pulsed LASER deposition (PLD) technique. These thin films were then compared to Fe thin films of same thickness deposited under similar conditions. Using inversion of spectroscopic transmittance and reflectance spectra in the wavelength range 300-2500nm, optical constant ε2(imaginary part of dielectric constant) was found. The optical properties resemble those of other transition metals and their alloys, being mainly determined by interband transitions in the studied wavelength range. The free electron contribution is not significant in this region, which is in line with their low electrical conductivity. These thin films also show large moment (~372.5emu/cc) and soft magnetic properties (coercivity of ~15 Gauss). Being glassy in nature, they can be easily fabricated on any kind of substrate and can tolerate high temperatures (Glass transition temperature for bulk material is close to 700°C [1]) without changing physical properties. Epitaxial and defect free growth of thin films are critical parameters for thin film fabrication. These can be avoided using amorphous materials hence (Fe72B24Nb4)95.5Y4.5 thin films has potential for new functional thin film structures and composites for magneto-optic applications.
|
|
| 10. |
- Nagar, Sandeep
(författare)
-
Beginning julia programming : For engineers and scientists
- 2017
-
Bok (övrigt vetenskapligt/konstnärligt)abstract
- Get started with Julia for engineering and numerical computing, especially data science, machine learning, and scientific computing applications. This book explains how Julia provides the functionality, ease-of-use and intuitive syntax of R, Python, MATLAB, SAS, or Stata combined with the speed, capacity, and performance of C, C++, or Java. You’ll learn the OOP principles required to get you started, then how to do basic mathematics with Julia. Other core functionality of Julia that you’ll cover, includes working with complex numbers, rational and irrational numbers, rings, and fields. Beginning Julia Programming takes you beyond these basics to harness Julia’s powerful features for mathematical functions in Julia, arrays for matrix operations, plotting, and more. Along the way, you also learn how to manage strings, write functions, work with control flows, and carry out I/O to implement and leverage the mathematics needed for your data science and analysis projects. “Julia walks like Python and runs like C”. This phrase explains why Julia is quickly growing as the most favored option for data analytics and numerical computation. After reading and using this book, you’ll have the essential knowledge and skills to build your first Julia-based application. What You’ll Learn Obtain core skills in Julia Apply Julia in engineering and science applications Work with mathematical functions in Julia Use arrays, strings, functions, control flow, and I/O in Julia Carry out plotting and display basic graphics. Who This Book Is For Those who are new to Julia; experienced users may also find this helpful as a reference.
|
|
