09 - Magnetic properties

Question 1

two main ffects due to magnetic field

Answer 1

1. induced magnetization

2. remanent magnetization

Question 2

1. induced magnetization

Answer 2

magnetic field is applied to a material with a magnetic susceptibility

Question 3

2. remanent magnetization

Answer 3

exists regardless of field

occurs within ferri & ferromagnetic substances

Question 4

1. induced magnetization

volume susceptibility kappa

Answer 4

kappa = material magnetization M / magnetic field strength H

Question 5

1. induced magnetization

mass susceptibility kappa_g

Answer 5

kappa_g = kappa / rho

Question 6

Magnetic induction

Answer 6

B = mü0müH

B = mü0 * (H+M)

B = mü0 * (1+k) * H

Question 7

Diamagnetism

Answer 7

create magnetic field in opposition to external field

only in applied field!

low neg. magn. susceptibility

Question 8

Diamagnetic minerals

Answer 8

Calcite, Dolomite

Quartz

Fluorite, Halite, Anhydrite

Orthoclase

Question 9

Paramagnetic

Answer 9

create magnetic field in direction of external field

only in applied field!

pos. susceptibility (10^-4 - 10^-2)

inversely propertional to abs. T

Question 10

Paramagnetic

minerals

Answer 10

Olivine, Amphibole, Pyroxene
Micas, Illite Chlorite

Dolomite

Question 11

Ferro-, Antiferro-, and Ferrimagnetic Materials

Answer 11

Ferro AAAAA - parallel
Ferri AvAvA - antiparallel intrinsic moments
Aniferro AVAVAV - equal but antiparallel

high pos. susceptibility

remanent magnetization

Question 12

Ferro-, Antiferro-, and Ferrimagnetic Materials

dependencies

Answer 12

1. temperature
   T higher than T_c: Paramagnetic properties M = Mi + Mr
2. field strength
3. magnetic history (hysteresis loop)

Question 13

Ferro-, Antiferro-, and Ferrimagnetic Materials

Koenigsberger Q ratio

Answer 13

Q= Mr/Mi= Mr / (kappa*H)

induced magnetization Mi
remanet magnetization Mr

Question 14

Ferro-, Antiferro-, and Ferrimagnetic Materials

minerals

Answer 14

Titanomagnetites (igneous)

Magnetite (igneous, metamorphic, sedimentary)

Hematite (sediments,igneous)

Ilmenite (metamorphic)

Pseutobrookite (igneous metamorphic)

Pyrrhotite

Goethite

Question 15

Magnetic properties depend on

Answer 15

chemical inhomogeneity

depositional

crystallization

post formational conditions

ferrimagnetic minerals

Question 16

Susceptibility

Sediments

Granites gneisses

intrusive basic rocks

Answer 16

Sediments:
kappa <10^-4

Granites gneisses:
kappa = 10^-4 - 10^-3

intrusive basic rocks:
kappa >10^-3

Question 17

TRM

Answer 17

Thermoremanent magnetization

remanence acquired by a rock, when it is cooled from T above T_c to lower T

Q > 1

Question 18

CRM

Answer 18

Chemical remanent magnetization

during formation of magnetic mineral

related to processes
such as oxidation, dehydration, precipitation, recrystallization

Question 19

DRM

Answer 19

Detrital/ Depositional remanent magnetization

oriented deposition of previously magnetized mineral grains

depend on depositional env. (low turbuleces) & sediment type (clays)

marine sediments, lake, varved clays

(post-depositional remanent magnetization PDRM)