Anomalous Perpendicular Anisotropy in Ultra-Thin Co Films

1993 ◽  
Vol 313 ◽  
Author(s):  
Michael H. Wiedmann ◽  
Brad N. Engel ◽  
Robert A. Van Leeuwen ◽  
Ko Mibu ◽  
Teruya Shinjo ◽  
...  
Keyword(s):  
Transition Metal ◽  
Kerr Effect ◽  
Atomic Layer ◽  
Perpendicular Anisotropy ◽  
Magnetic Metal ◽  
Layer 2 ◽  
Polar Kerr Effect ◽  
Total Coverage ◽  
Peak Value

ABSTRACTWe have used in situ polar Kerr effect measurements to study the magnetic coercivity and anisotropy of MBE-grown Pd (111) /Co/X and Au (111) /Co/X trilayers, where χ is the nonmagnetic noble or transition metal overlayer Ag, Cu or Pd. Polar hysteresis curves were Measured in situ for systematically varied Co and overlayer thicknesses 2 Å ≤ tco ≤ 20 Å and 0 Å ≤ tx ≤ 50 Å. We find the coercivity and total anisotropy display a strongly peaked perpendicular contribution at ∼1 atomic layer (2 Å) non-Magnetic Metal coverage. For Cu, where the effect is strongest, the total anisotropy energy rapidly decreases by a factor of 3 from its peak value after a total coverage of ∼2 atomic layers (4 A) of Cu.

Unusual Behavior in The Magnetic Anisotropy of Ultra-Thin Co Sandwiches: The Role of Au Underlayers.

1995 ◽  
Vol 384 ◽  
Author(s):  
Christian Marlière ◽  
Brad N. Engel ◽  
Charles M. Falco
Keyword(s):  
Magnetic Anisotropy ◽  
Coercive Field ◽  
Kerr Effect ◽  
Atomic Layer ◽  
Perpendicular Anisotropy ◽  
Unusual Behavior ◽  
Sharp Minimum ◽  
Polar Kerr Effect

ABSTRACTWe have used in situ polar Kerr effect measurements to study the magnetic anisotropy of X/Co/Y sandwich structures grown by MBE on Cu(111) buffers, where X and Y are variable thicknesses of Au. For fixed values of Y and in the case of an underlayer wedge, e.g. variable X value, we have found a sharp minimum in both coercive field and perpendicular anisotropy at ≈1 atomic layer of the Au underlayer. This anisotropy behavior is opposite to that of an Au overlayer deposited on a Co film, i.e. variable Y and fixed X.

PROPERTIES OF MBE-GROWN SUPERLATTICES AND ULTRA-THIN FILMS

1993 ◽  
Vol 07 (01n03) ◽  
pp. 446-451
Author(s):  
CHARLES M. FALCO ◽  
BRAD N. ENGEL
Keyword(s):  
Lattice Spacing ◽  
Molecular Beam ◽  
Magnetic Transition ◽  
Magnetic Behavior ◽  
Atomic Layer ◽  
High Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Layer 2

We have used Molecular Beam Epitaxy (MBE) to grow single-crystal Co/Pd superlattices and Co/TM (TM=Cu, Pd, Ag) bilayers and sandwiches along the three high-symmetry crystal directions; [001], [110], and [111]. In the case of Co/Pd superlattices, we previously reported from x-ray diffraction measurements that for small Co thicknesses the (001) oriented superlattices are coherently strained in-plane to near the bulk Pd lattice spacing. This strain leads to a very large in-plane magnetoelastic volume anisotropy for these superlattices. Here we report quantitative in situ RHEED measurements of Co deposited on Pd (001) that confirm this coherently strained growth. We have also used in situ polar Kerr ellipticity measurements to study the perpendicular magnetic behavior of Pd/Co/TM (111) sandwich structures, where TM is the non-magnetic transition metal overlayer Ag, Cu or Pd. We observed perpendicular loops with coercive fields of H c ≤ 200 Oe for the uncovered Co films for t co ≤ 6 Å, becoming in-plane above this thickness. However, subsequent deposition of just one atomic layer (≈ 2 Å) of any of the TM over the Co resulted in strongly perpendicular, square hysteresis curves with H c ≥ 900 Oe for all films in the Co thickness range studied.

Methane activation by ZSM-5-supported transition metal centers

2021 ◽  
Author(s):  
Daniyal Kiani ◽  
Sagar Sourav ◽  
Yadan Tang ◽  
Jonas Baltrusaitis ◽  
Israel E. Wachs
Keyword(s):  
Transition Metal ◽  
Methane Activation ◽  
Group V ◽  
Metal Centers ◽  
Methane Dehydroaromatization

The literature on methane dehydroaromatization (MDA) to benzene using ZSM-5 supported, group V–VIII transition metal-based catalysts (MOx/ZSM-5) is critically reviewed with a focus on in situ and operando molecular insights.

Atomic Layer Deposition of LiF and Lithium Ion Conducting (AlF3)(LiF)x Alloys Using Trimethylaluminum, Lithium Hexamethyldisilazide and Hydrogen Fluoride

2017 ◽  
Author(s):  
Younghee Lee ◽  
Daniela M. Piper ◽  
Andrew S. Cavanagh ◽  
Matthias J. Young ◽  
Se-Hee Lee ◽  
...  
Keyword(s):  
Lithium Ion ◽  
Atomic Layer ◽  
Mass Gain ◽  
Alloy Film ◽  
Ex Situ ◽  
X Ray ◽  
Layer Deposition ◽  
Ion Conducting ◽  
Good Agreement

<div>Atomic layer deposition (ALD) of LiF and lithium ion conducting (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloys was developed using trimethylaluminum, lithium hexamethyldisilazide (LiHMDS) and hydrogen fluoride derived from HF-pyridine solution. ALD of LiF was studied using in situ quartz crystal microbalance (QCM) and in situ quadrupole mass spectrometer (QMS) at reaction temperatures between 125°C and 250°C. A mass gain per cycle of 12 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C and decreased at higher temperatures. QMS detected FSi(CH<sub>3</sub>)<sub>3</sub> as a reaction byproduct instead of HMDS at 150°C. LiF ALD showed self-limiting behavior. Ex situ measurements using X-ray reflectivity (XRR) and spectroscopic ellipsometry (SE) showed a growth rate of 0.5-0.6 Å/cycle, in good agreement with the in situ QCM measurements.</div><div>ALD of lithium ion conducting (AlF3)(LiF)x alloys was also demonstrated using in situ QCM and in situ QMS at reaction temperatures at 150°C A mass gain per sequence of 22 ng/(cm<sup>2</sup> cycle) was obtained from QCM measurements at 150°C. Ex situ measurements using XRR and SE showed a linear growth rate of 0.9 Å/sequence, in good agreement with the in situ QCM measurements. Stoichiometry between AlF<sub>3</sub> and LiF by QCM experiment was calculated to 1:2.8. XPS showed LiF film consist of lithium and fluorine. XPS also showed (AlF<sub>3</sub>)(LiF)x alloy consists of aluminum, lithium and fluorine. Carbon, oxygen, and nitrogen impurities were both below the detection limit of XPS. Grazing incidence X-ray diffraction (GIXRD) observed that LiF and (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film have crystalline structures. Inductively coupled plasma mass spectrometry (ICP-MS) and ionic chromatography revealed atomic ratio of Li:F=1:1.1 and Al:Li:F=1:2.7: 5.4 for (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film. These atomic ratios were consistent with the calculation from QCM experiments. Finally, lithium ion conductivity (AlF<sub>3</sub>)(LiF)<sub>x</sub> alloy film was measured as σ = 7.5 × 10<sup>-6</sup> S/cm.</div>

In Situ Ultrafast and Patterned Growth of Transition Metal Dichalcogenides from Inkjet‐Printed Aqueous Precursors

2021 ◽  
pp. 2100260
Author(s):  
Xi Wan ◽  
Xin Miao ◽  
Jie Yao ◽  
Shuai Wang ◽  
Feng Shao ◽  
...  
Keyword(s):  
Transition Metal ◽  
Transition Metal Dichalcogenides ◽  
Patterned Growth ◽  
Metal Dichalcogenides

scholarly journals Resolving the Evolution of Atomic Layer-Deposited Thin-Film Growth by Continuous In Situ X-Ray Absorption Spectroscopy

2021 ◽  
Author(s):  
Xiaohui Qu ◽  
Danhua Yan ◽  
Ruoshui Li ◽  
Jiajie Cen ◽  
Chenyu Zhou ◽  
...  
Keyword(s):  
Thin Film ◽  
Absorption Spectroscopy ◽  
Film Growth ◽  
Atomic Layer ◽  
Thin Film Growth ◽  
X Ray ◽  
X Ray Absorption

Insertion Reaction of 2-Halo-N-allylanilines with K2S Involving Trisulfur Radical Anion: Synthesis of Benzothiazole Derivatives under Transition-Metal-Free Conditions

Synthesis ◽  
2020 ◽  
Author(s):  
Yan-Wei Zhao ◽  
Shun-Yi Wang ◽  
Xin-Yu Liu ◽  
Tian Jiang ◽  
Weidong Rao
Keyword(s):  
Transition Metal ◽  
Radical Anion ◽  
Radical Cyclization ◽  
Transition Metal Catalysis ◽  
Insertion Reaction ◽  
Metal Catalysis ◽  
Metal Free ◽  
Benzothiazole Derivatives

AbstractA synthesis of benzothiazole derivatives through the reaction of 2-halo-N-allylanilines with K2S in DMF is developed. The trisulfur radical anion S3·–, which is generated in situ from K2S in DMF, initiates the reaction without transition-metal catalysis or other additives. In addition, two C–S bonds are formed and heteroaromatization of benzothiazole is triggered by radical cyclization and H-shift.

Rheed Studies of a-Axis Oriented DyBa2Cu3O7 Films Grown by All-MBE

1997 ◽  
Vol 502 ◽  
Author(s):  
Ivan Bozovic ◽  
J. N. Eckstein ◽  
Natasha Bozovic ◽  
J. O'Donnell
Keyword(s):  
Phase Transitions ◽  
Secondary Phase ◽  
Atomic Layer ◽  
High Energy ◽  
Layer By Layer ◽  
Growth Modes ◽  
Flow Surface ◽  
Surface Phase Transitions

ABSTRACTReal-time, in-situ surface monitoring by reflection high-energy electron diffraction (RHEED) has been the key enabling component of atomic-layer-by-layer molecular beam epitaxy (ALL-MBE) of complex oxides. RHEED patterns contain information on crystallographic arrangements and long range order on the surface; this can be made quantitative with help of numerical simulations. The dynamics of RHEED patterns and intensities reveal a variety of phenomena such as nucleation and dissolution of secondary-phase precipitates, switching between growth modes (layer-by-layer, step-flow), surface phase transitions (surface reconstruction, roughening, and even phase transitions induced by the electron beam itself), etc. Some of these phenomena are illustrated here, using as a case study our recent growth of atomically smooth a-axis oriented DyBa2Cu3O7 films.

Transition-Metal-Free Cascade Approach toward 2-Alkoxy/2-Sulfenylpyridines and Dihydrofuro[2,3-b]pyridines by Trapping In Situ Generated 1,4-Oxazepine

2017 ◽  
Vol 82 (18) ◽  
pp. 9515-9524 ◽  
Author(s):  
Guolin Cheng ◽  
Lulu Xue ◽  
Yunxiang Weng ◽  
Xiuling Cui
Keyword(s):  
Transition Metal ◽  
Metal Free
Sign in / Sign up

Export Citation Format

Share Document