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Concept tests
Leon Abelmann leon.manucodiata.org
THE EUROPEAN SCHOOL ON
https://youtu.be/Z9orbxoRofI
Peer instruction for active learning
MAGNETISM Concept tests Leon Abelmann leon.manucodiata.org Peer - - PowerPoint PPT Presentation
MAGNETISM Concept tests Leon Abelmann leon.manucodiata.org Peer - - PowerPoint PPT Presentation
THE EUROPEAN SCHOOL ON MAGNETISM Concept tests Leon Abelmann leon.manucodiata.org Peer instruction for active learning https://youtu.be/Z9orbxoRofI A THE EUROPEAN SCHOOL ON MAGNETISM The H field Spontaneous magnetisation
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The H field Spontaneous magnetisation Direct exchange
Leon Abelmann
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THE EUROPEAN SCHOOL ON
MAGNETISM
A
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A (purple) B (blue) C (green) D (orange) : magnetisation at constant volume : volume at constant moment : moment at constant magnetisation : magnetisation at constant moment To increase the field far away from a permanent magnet I can increase:
Multiple answers possible
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SLIDE 5
(purple) (blue) (green) (orange)
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R
I I
B H H B H H H H H H A B C D
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A (purple) B (blue) C (green) D (orange) : 0 0 : 0 Minimum : Maximum 0 : Maximum Minimum Probability of finding the electron in the nucleus
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A
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(purple) (blue) (green) Uniformly magnetised bar magnet
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E
M B H M B H M B H A B C B=μ0(H+M)
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A (red) B (blue) C (green)
- +
H-atom
- rbital moment
(pointing at you) (pointing from you)
B
B
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A (purple) B (blue) C (green) : H in x is parallel to M : H in x is anti-parallel to M : H = 0 Hole in a permanent magnet with magnetisation M
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M x M
D
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- +
H + H+
- +
- +
H2 A (purple) B (blue) C (green) : mH+ ≥ mH : mH+ ≥ mH2 : mH ≥ mH2
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C
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A (purple) B (blue) C (green) D (orange) Fe2+: [Ar] 3d4 4s2 Fe2+: [Ar] 3d5 4s1 Fe2+: [Ar] 3d6 4s0 None of the above Hunds rule: Mn: [Ar] 3d5 4s2 Fe: [Ar] 3d6 4s2 Co: [Ar] 3d7 4s2
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F
Ionized Fe:
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G
O Mn Mn [He] 2s22p4 [Ar] 3d54s2 2p: A (red) B (blue) C (green) O2- Mn2+ O O O2- Mn2+ O2- [He] 2s22p6 [Ar] 3d5 2p: 3d:
1 2 1 2
3d: 3d:
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Anti-ferro and ferri-magnetism Anisotropy - phenomenological Anisotropy - pair model
Leon Abelmann
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THE EUROPEAN SCHOOL ON
MAGNETISM
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A (purple) B (blue) C (green) D (orange) : down : up : zero : None of the above
x B in x: B=0 A B C cubic
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H
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A (purple) B (blue) C (green) : Ep > Ea : Ep < Ea : Ep = Ea
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p a B
I
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A (purple) B (blue) C (green) D (orange) : Mn has a half filled d-shell : Mn oxidises too fast : Mn is an anti-ferromagnet : Another reason Mn: [Ar] 3d5 4s2 is not a ferromagnet because:
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J
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A (purple) B (blue) C (green) D (orange) : Para-, Ferro-, Anti-ferro : Anti-ferro-, Para-, Ferromagnetic : Para-, Anti-ferro, Anti-ferro : Ferro-, Anti-ferro, Para
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K
T T T 1
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Image from Rajat Roy
A (purple) B (blue) C (green) D (orange) : Cr chemically reacts with Ni, Co : Cr couples anti-ferromagnetically : All of the above : None of the above Effect Cr on Fe different from Co and Ni because:
Fe-Cr Co-Cr 100%Fe 100%Cr 100%Co 100%Ni
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L
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A (purple) B (blue) C (green) D (orange) : 0 : 45 : 90 : 135 𝛥=-dE/d𝜄
θ
45 90 135 180
Γ
The easy axis is at 𝜄=
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M
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A (purple) B (blue) C (green) : Ku1 increases : Ku1 decreases : Ku1 = 0
θ
a b
θ
a b
E=Ku1 cos2(𝜄) + K2 cos2(2𝜄) First b/a=1, if I increase b/a, then
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N
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A (purple) B (blue) C (green) D (orange)
A K1 K2 Ktot B Ktot C Ktot Ktot=0 D
K1, K2 uni-axial
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O
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A (purple) B (blue) C (green) : K1 less T-dependent : K1 same as Ku1
: K1 more T-dependent
Uni-axial: E=Ku1 cos2(𝜄) Cubic: E=K1 (𝛽12𝛽22+𝛽12𝛽32+𝛽22𝛽32) If T-dependence Ku1 is as indicated, than K1
T/Tc 1
M
Ku1 A B C
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P
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: K2 increases but K2 <0 : K2 increases (K2 >0 is ok) : K2 decreases but K2 >0 : K2 decreases (K2 <0 is ok)
θ
a b
θ
a b
E=Ku1 cos2(𝜄) + K2 cos2(2𝜄) If I increase b/a, then A (purple) B (blue) C (green) D (orange)
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Q