Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

382: Environmental Magnetism > 1-2: Basic Principles of Magnetism > Flashcards

1-2: Basic Principles of Magnetism Flashcards

1
Q

What defines diamagnetic behavior?

A

Spin and orbital moments cancel – no net moment

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What defines paramagnetic behavior?

A

Possesses spin magnetic moment as well as orbital magnetic moment, only partial cancellation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What occurs to a paramagnetic material with increasing temperature?

A

Magnetisation decreases as temperature increases

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What defines ferromagnetic behavior?

A

Spin and orbital moments do not cancel, exchange coupling occurs

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is exchange coupling in terms of magnetism?

A

Adjacent atoms are close in crystal lattice so electron orbitals overlap and strong interaction occurs.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What is the arrangement of ferromagnetic behavior?

A

Regular arrows in a parallel direction, all same length.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What is the arrangement of antiferromagnetism?

A

Atoms have same strength but neighboring atoms have oppositely directed moments – zero net magnetisation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

When does net magnetism occur in antiferromagnetic materials?

A

If there is damage or deficit to crystal lattice

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What is the arrangement of ferrimagnetic behavior?

A

Opposing directions, but different strengths so there is a net magnetic direction.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Give an example of a ferrimagnetic mineral, and its chemical composition.

A

Magnetite, Fe3O4.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

What is “canted” antiferromagnetism?

A

When the directions are equal and opposite, but slightly turned in on direction or the next, such as /\/\/ all pointing right.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Give an example of a canted antiferromagnetic mineral, and its chemical composition.

A

Haematite, Fe2O3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Why are paramagnets so un-magnetic at room temperature?

A

Thermal energy at room temperature disrupts alignment thousands of times more than magnetic energy trying to align the moments.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Paramagnets need either ___ or ____ to be magnetized.

A

Very low temperatures or very high magnetic fields

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What would the graph for M vs H look like for a paramagnet?

A

Linear and close to the origin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

What happens when the external field is removed from diamagnets and paramagnets?

A

Magnetisation disappears

17
Q

What happens to a ferromagnetic material when a sample is saturated, and then the field is reduced back to zero?

A

The sample is left with a permanent magnetization, called saturated magnetic remanence.

18
Q

What happens when a negative field is implemented on a sample with magnetic remanence?

A

It can become negatively saturated.

19
Q

The act of saturating a ferromagnet in one direction, and then the opposite creates a ___ ___.

A

Hysteresis Loop

20
Q

What is the difference between remanence and saturation remanence?

A

Remanence occurs when the sample has been magnetically reversed before reaching saturation, saturation remanence is therefore the maximum amount of remanence the sample can hold.

21
Q

How do you spell the R from SIRM?

A

REM-AN-ENCE

22
Q

What is the coercive force?

A

Hc, the point where a sample with saturation remanence has been reversed to the point where M = 0.

23
Q

How does one return the sample to the origin where H = 0 and M = 0?

A

Apply coercivity of remanence (Hcr) – a negative magnetic field of Hcr must be applied, where at the point of Hcr, if a positive field was applied, the sample would pass back through the origin.

24
Q

Why is Mrs always smaller than Ms?

A

The ferromagnet is divided into small regions where magnetisation is uniform within the region, but the vector of each region differs from its neighbor.

25
Q

What is the name of the magnetic regions within a ferromagnet?

A

Magnetic domains

26
Q

What is the name of a mineral grain containing many magnetic regions?

A

Multi-domain (MD)

27
Q

What is the name of a mineral grain containing one magnetic region?

A

Single-domain (SD)

28
Q

What is the name for grains which contain only a few magnetic regions?

A

Pseudo-single-domain (PSD), a middle ground between MD and SD

29
Q

What are the two basic magnetic properties of super-paramagnetic grains?

A

Large susceptibility, does not retain remanence

30
Q

Name the six major sources of Magnetite

A

Igneous, Metamorphic, Recycled in sedimentary, Top-soils, Some organisms, Combustion processes.

31
Q

Name the four major sources of Haematite

A

Igneous, Metamorphic, Sedimentary, Some soils

32
Q

Name the two major sources of Goethite

A

Sedimentary, Some soils

33
Q

Name the one major source of Greigite

A

Sedimentary

34
Q

Give three environmental reasons for changes in SIRM and χ

A

Different magnetite concentrations, different sediment sources, different transportation processes

382: Environmental Magnetism (7 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions