Magnetism Flashcards
alternative to magnetic induction for the fundamental magnetic field vector B
Magnetic Flux Density
Wrote the earliest known experimental physics
Petrus Peregrinus (Willian Gilbert)
The book written by W. GIlbert about the earliest known treatise of fundamental physics
de Magnete
the reason why magnetic compasses did not point exactly to the geographical north
Magnetic Declination
Geomagnetism and Paleomagnetism declination was the principal cause of error in map making.
Mercator
Theorized The magnetized needle assumed a non horizontal attitude in the vertical plane
Georg Hartmann
The deviation from the horizontal
Magnetic inclination
continuous drift in the intensity and direction of the field. reflects changes in the earth’s interior over time
Secular Variation
observed that magnetic needle is deflected at right angles to conductor carrying a current; electrical current produces magnetic force
Hans Christian Oersted
proposed that electrical currents were responsible for the existence of magnetism in iron objects
Ampere
Magneto electric induction
M. Faraday
static magnetism was carried by magnetic charges
C. F. Gauss
Magnetic Declination: compass points to the east
positive
Magnetic Declination: compass points to the east
negative
declination value is constant
isogonic lines
lines along declination value is zero
Agonic Lines
Angle formed between the earth’s surface and planet’s magnetic lines
Magnetic Declination
Mag Inclination: Upward
-
Mag inclination downward
+
property of material that are repelled by a magnetic field
Diamagnetic
Diamagnetic Minerals
Quartz, Calcite
Parallel to the magnetic field but weak attraction, susceptibility is reversible, small and positive.
Paramagnetism
weakly attracted to magnetic field
Paramagnetism
Magnetization of a paramagnetic material is directly proportional to the applied magnetic field (B) and inversly proportional to the Temperature (T) in Kelvin
Curie’s Law
Examples of Paramagnetic Minerals
Clay minerals, chlorite, amphibole, px, olivine
becomes magnetized and remains magnetized
Ferromagnetism
Residual magnetization is called
Remanence (Isothermal Remanent Magnetization)
When a ferromagnetic material is heated, its spontsnrous magnetization dissapears at ______
Curie Temp
Mag moments align antiparallel to each other. This alignment leads to cancellation of the magnetic moments
Antiferromagnetism
Mineral: Antiferromagnetism
llmenite
temp at which an antiferromagnetic material undergoes a phase transition from an ordered state (A-Ferromagntism) to disordered state (Paramagnetic State)
Neel Temperature
Crystals contains defects, vacancies, or impurites
Parasitic Ferromagnetism
Example of parasitic ferromagnetism mineral
hematite
Antiparallel and unequal in magnitude. Net magnetic moment smaller than that of ferromagnetic material
Ferrimagnetism
Mineral: Ferrimagnetism
Magnetite
Magnetic behavior is not uniform in all directions but depends on the orientation with respect to a preferred axis.
Magnetic Anisotropy
Matrix minerals are mainly composed of
Silicates and Carbonates
Silicates and Carbonates exhibits what magnetism
Diamagnetic
Secondary minerals
CLay minerals, paramagnetic
Magnetic property of rock is determined by_________
concentration of ferrimagnetic minerals
The most important magnetic minerals and ar naturally occurring ferrites
Iron-titanium oxides
low-temperature oxidation of titanomagnetite
Titanomaghemite
T or F: Hematite in a higher state of oxidation than wustite
True
Close-packed lattice of oxygen ions, in which some of the interstitial spaces are occupied by regular arrays of ferrous (Fe2+) and ferric (Fe3+) iron ions and titanium (Ti4+) ions
iron–titanium oxides
When there’s more titanium (x) in these minerals on the he Titanomagnetite Series, cell size _____, curie temperature ______.
Increases, decreases
referred to as “hemoilmenite,” “hematite-ilmenite” or “ilmenohematite
have the general formula Fe2–xTixO3 where compositional parameter x has the same implications for the titanium content of the unit cell
Titanohematite Series
Third series but quite rare and are of minor importance in rock magnetism. paramagnetic at room temperature
Pseudobrookite
on Neel Temperature
antiferromagnetism disappears is around ______
320 C
As Ti content increases, spontaneous magnetization________
decreases
Which of the following minerals have the lowest Curie temperature?
a. hematite b. goethite c. maghemite d. magnetite
C. Maghemite
A remanence acquired at or close to the time of formation of the rock is called a
Primary Magnetization
a remanence acquired at a
later time is called a
Secondary Magnetization
The most important type of remanent magnetization in igneous
thermoremanent magnetization (TRM).
Occurs when rock cools below Curie temperature of ferrimagnetic minerals
Thermoremanent magnetization (TRM)
Acquired during settling through still water
Particles align with ambient magnetic field similar to a compass needle
Sedimentary remanent magnetization
T or F : TRM is a very
unstable magnetization which can exist unchanged for long intervals of geological time.
False
may be caused by chemical change of the rock during diagenesis or
weathering, or by sampling and laboratory procedures.
Secondary remanences
is formed when the magnetic minerals in a rock suffer
chemical alteration or when new minerals form authigenically.
Chemical remanent magnetization
induced in a rock sample by placing it in a
magnetic field at constant temperature.
Isothermal remanent magnetization (IRM)
arises when a material undergoes mechanical
deformation while in a magnetic field. The process of deformation may result from hydrostatic
pressure, or directed tectonic stress.
Piezoremanent magnetization (PRM)
shock remanent magnetization (SRM)
observed in
Meteor impacts
Piezoremanent magnetization (PRM) arises when a material undergoes mechanical
deformation while in a magnetic field. The process of deformation may result from hydrostatic
pressure, or directed tectonic stress.
Primary
Secondary of Primary: Anhysteretic remanent magnetization (ARM) can be produced in a rock sample by placing it
in a coil that carries an alternating magnetic field, whose amplitude is then slowly reduced to
zero.
Secondary
Primary or Secondary: Piezoremanent magnetization (PRM) arises when a material undergoes mechanical
deformation while in a magnetic field.
Primary
