The Erieau Excursion revisited

1993 ◽  
Vol 30 (8) ◽  
pp. 1741-1748 ◽  
Author(s):  
W. A. Morris ◽  
C. M. Carmichael
Keyword(s):  
Magnetic Field ◽  
Lake Erie ◽  
Magnetic Transition ◽  
Paleomagnetic Data ◽  
Geomagnetic Excursion ◽  
Regional Deformation ◽  
Remanence Direction ◽  
Glaciogenic Sediments ◽  
Stratigraphic Boundary

Paleomagnetic results from two cores collected from the central and eastern basins of Lake Erie contain the same remanence direction shift from positive to negative inclination at a depth of approximately 9 m. Confirmation of the existence of this boundary over a wider extent of Lake Erie may initially appear to support the interpretation of this feature as the record of a geomagnetic excursion: the Erieau Excursion. Many details in the paleomagnetic record of these cores indicate that this feature is not of geomagnetic origin: the lack of synchroneity of this event across the lake; the association of the reversed directions with deformed sediments; the lack of any record of the transitional magnetic field; and the absence of any correlation between the reversed directions from the two cores. In core EK, the apparent magnetic transition is coincident with the stratigraphic boundary between the lacustrine and glaciogenic sediments. The model most compatible with this new paleomagnetic data involves regional deformation of the substrate of Lake Erie by some mechanism prior to 9500 years ago. The most likely mechanism to have produced this regional deformation was subglacial deformation of the underlying sediments.

CRITICAL FIELD AND MAGNETORESISTANCE OF SINGLE CRYSTAL TmNi2B2C

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3715-3717 ◽  
Author(s):  
D. G. NAUGLE ◽  
K. D. D. RATHNAYAKA ◽  
K. CLARK ◽  
P. C. CANFIELD
Keyword(s):  
Magnetic Field ◽  
Transition Temperature ◽  
Single Crystal ◽  
Critical Field ◽  
Superconducting Transition Temperature ◽  
Magnetic Transition ◽  
Upper Critical Field ◽  
Superconducting Transition ◽  
Large Anisotropy ◽  
The Magnetic Field

In-plane resistance as a function of magnitude and direction of the magnetic field and the temperature has been measured for TmNi2B2C from above the superconducting transition temperature at 10.7 K to below the magnetic transition TN=1.5 K. The superconducting upper critical field HC2(T) exhibits a large anisotropy and structure in the vicinity of TN. The magnetoresistance above TC is large and changes sign as the direction of the magnetic field is rotated from in-plane to parallel with the c-axis.

Synthesis of palaeomagnetic datasets suggests that the geomagnetic field was persistently non-uniformitarian in the Devonian

2021 ◽  
Author(s):  
Annique van der Boon ◽  
Andy Biggin ◽  
Daniele Thallner ◽  
Mark Hounslow ◽  
Jerzy Nawrocki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Weak Field ◽  
Paleomagnetic Data ◽  
Independent Evidence ◽  
Tectonic Plates ◽  
Polar Wander ◽  
Push Forward ◽  
Geomagnetic Polarity ◽  
Life On Earth ◽  
Geomagnetic Polarity Time Scale

<p>The Devonian has long been a problematic era for paleomagnetism. Devonian data are generally difficult to interpret and have complex partial or full overprints. These problems arise from paleomagnetic data obtained from both sedimentary and igneous rocks. As a result, the reconstruction of motions of tectonic plates is often troubling, as these rely on apparent polar wander paths constructed from Devonian paleomagnetic poles. Also the geomagnetic polarity time scale for this time period is poorly constrained. Paleointensity studies suggest that the field was much weaker than the field of today, and it has been hypothesised that this was accompanied by many polarity reversals (a hyperreversing field). We review studies on Devonian paleopoles, magnetostratigraphy and paleointensity. We tentatively suggest that the field during the Devonian might have been so weak and perhaps of a non-dipolar configuration, that obtaining reliable paleomagnetic data from Devonian rocks is extremely difficult.  In order to push forward the understanding of the Devonian field, we emphasise the need for studies to provide fully accessible data down to specimen level demagnetisation diagrams. Incorporating all data, no matter how complex or bad they might seem, is the only way to advance the understanding of the Devonian magnetic field. Recent paleointensity studies appear to suggest that the Devonian and Ediacaran were both extreme weak field intervals. For the Ediacaran, it has been hypothesised that the field had an impact on life on earth. A fundamentally weak and perhaps non-dipolar field during the Devonian might have had an influence on evolution and extinctions. As there is a large number of biological crises in the Devonian, we here pose the question whether the Earth’s magnetic field was a contributing factor to these crises. New independent evidence from the Devonian-Carboniferous boundary suggests that the Hangenberg event was caused by increased UV-B radiation, which is in line with a weak magnetic field.</p>

Devonian magnetostratigraphy: new data and old problems

2021 ◽  
Author(s):  
Annique van der Boon ◽  
Andy Biggin ◽  
Daniele Thallner ◽  
Mark Hounslow ◽  
Jerzy Nawrocki ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Scale ◽  
Age Determination ◽  
Paleomagnetic Data ◽  
Show Evidence ◽  
Reversal Frequency ◽  
Geomagnetic Polarity ◽  
Geomagnetic Polarity Time Scale

<p>The global polarity time scale (GPTS) is relatively unconstrained for the Paleozoic, particularly the Devonian. Constraining the GPTS and reversal frequency for the Devonian is crucial for the understanding of the behaviour of Earth’s magnetic field. Furthermore, construction of a GPTS for the Paleozoic could provide a valuable tool for age determination in other studies. However, most paleomagnetic data from the Devonian is problematic. The data are difficult to interpret and don’t have a single easy to resolve (partial or full) overprint. Paleointensity studies suggest that the field was much weaker than the field of today, which could have been accompanied by many reversals (a hyperreversing field). In order to improve the geomagnetic polarity time scale in the Devonian, and quantify the number of reversals in this time, we sampled three Devonian sections in Germany, Poland and Canada. These sections show evidence that the rocks were not significantly heated, and they show little evidence for remineralisation. This minimises the chance the rocks were remagnetised after the Devonian. Our data show that even when rocks are well qualified to have reliably recorded the Devonian field, the interpretation is not straightforward. We also discuss problems with the Devonian GPTS as presented in the geologic timescale.</p>

The Magnetocaloric Effect in Ni-Mn-X (X=Ga, in) Heusler Alloys and Manganites with Magnetic Transition close to Room Temperature

2010 ◽  
Vol 168-169 ◽  
pp. 165-168
Author(s):  
Vasiliy D. Buchelnikov ◽  
Mikhail Drobosyuk ◽  
E.A. Smyshlyaev ◽  
O.O. Pavlukhina ◽  
A.V. Andreevskikh ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetocaloric Effect ◽  
Room Temperature ◽  
Direct Method ◽  
Magnetic Transition ◽  
Heusler Alloys ◽  
Field Change ◽  
Adiabatic Temperature Change ◽  
Magnetic Field Change ◽  
The Magnetic Field

The magnetocaloric effect (MCE) in theNi2+xMn1-xGa (x = 0.33, 0.36, 0.39), Ni50Mn25In25, Ni54Mn21Ga18In7, Ni53.5Mn21.5Ga16In9, Ni45Co5Mn36.5In13.5 Heusler alloys and in the La0.7BayCa0.3-yMnO3 (y = 0.12, 0.24, 0.3) manganites at the Curie points have been measured by the direct method. For the magnetic field change H = 2 T, the maximal adiabatic temperature change Tad in the Ni2+xMn1-xGa alloys is larger than 0.6 K. For the Ni50Mn25In25 alloy the maximal value of Tad = 1.51 K (for the same magnetic field change H = 2 T) is observed at the magnetic phase transition temperature.

scholarly journals Magnetic Transition in La1/3Nd1/3Ca1/3MnO3Perovskite Induced by Electric Field at a Given Magnetic Field

2000 ◽  
Vol 97 (5) ◽  
pp. 879-882
Author(s):  
J. Baszyński ◽  
A. Kowalczyk ◽  
J. Kováč
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
Magnetic Transition

Untypical Temperature Dependence of the Magnetocaloric Effect in the Dy(Co1-xFex)2 (x = 0.10; 0.15) Compounds

2015 ◽  
Vol 233-234 ◽  
pp. 247-250 ◽  
Author(s):  
Maksim S. Anikin ◽  
Evgeniy N. Tarasov ◽  
Nikolay V. Kudrevatykh ◽  
Aleksander V. Zinin
Keyword(s):  
Magnetic Field ◽  
Temperature Dependence ◽  
Magnetic Entropy Change ◽  
Magnetic Transition ◽  
Iron Concentration ◽  
Entropy Change ◽  
Cooling Power ◽  
X Ray Diffraction ◽  
Magnetocaloric Properties ◽  
Ordered State

A study of crystalline structure, magnetic and magnetocaloric properties of Dy(Co1-хFeх)2 (х = 0.10, 0.15) intermetallic compounds was undertaken. Phase composition was controlled by X-ray diffraction analysis. Magnetic properties were measured with a help of SQUID magnetometer in magnetic fields up to 7 Т in the temperature range from 4.2 K to 400 K. Magnetic transition temperatures from paramagnetic to magnetically ordered state were inferred as 288 K and 350 K, respectively. It is shown that at an increase of iron concentration and/or magnetic field intensity, a considerable maximum broadenings on a temperature dependence of magnetic entropy change is observed. The calculated value of the relative cooling power (RCP) of Dy(Co0.90Fe0.10)2, in a magnetic field of 1.7 T is equal to 152 J/kg that is close to that for Gd metal with RCP = 181 J/kg at μ0Н = 2 T.

MAGNETIC PROPERTIES AND MAGNETOCALORIC EFFECT OF HYDROGEN TREATED Gd-BASED BULK METALLIC GLASS

2012 ◽  
Vol 26 (05) ◽  
pp. 1250041
Author(s):  
Q. ZHENG ◽  
H. FU ◽  
M. X. WANG
Keyword(s):  
Magnetic Field ◽  
Metallic Glass ◽  
Interatomic Distance ◽  
Magnetic Transition ◽  
Amorphous Structure ◽  
Magnetic Entropy ◽  
Magnetic Transition Temperature ◽  
Entropy Changes ◽  
The Magnetic Field ◽  
Absorption Of Hydrogen

The metallic glass Gd 52.5 Co 18.5 Al 28 Zr 1 preserves the amorphous structure after hydrogenation at 473 K for 48 h. The absorption of hydrogen leads to the reduction of the magnetic transition temperature due to the expansion of the interatomic distance. The magnetic anisotropy is introduced and the coercivity and remanence are 352 Oe and 12.5 emu/g at 1.8 K, respectively. The maxima of magnetic entropy changes are 11.3 and 7.5 J/kg K with the magnetic field changes of 0 to 70 kOe and 0 to 50 kOe, respectively. The decline of the magnetic entropy changes can be attributed to the disappearance of the collinear ferromagnetic characteristics and the difficulty of saturation for the magnetization after hydrogenation.

scholarly journals Influence of thermal annealing and magnetic field on first order magnetic transition in Pd substituted FeRh

2010 ◽  
Vol 200 (3) ◽  
pp. 032038 ◽  
Author(s):  
Pallavi Kushwaha ◽  
Archana Lakhani ◽  
R Rawat ◽  
P Chaddah
Keyword(s):  
Magnetic Field ◽  
Thermal Annealing ◽  
Magnetic Transition ◽  
First Order
Sign in / Sign up

Export Citation Format

Share Document