Ferromagnetism and antiferromagnetism • ferromagnetism (FM)
n σ 2 y Ni 2 d Co Fe Mn - Forsiden · Anti-ferro magnetism B Anti ferromagnetism occurs in...
6
Kap. 12 Magnetic solids What What is is magnetism magnetism ? ? What What is is magnetism magnetism ? ? http://www.uky.edu/~holler/orbitals/ d d xy xy d d yz yz d d xz xz n n σ σ ∗ ∗ ∆ ∆ 0 0 d d x x 2 2 - - y y 2 2 d d z z 2 2 Fe Co Ni Cr Mn What What is is magnetism magnetism ? ?
Transcript of n σ 2 y Ni 2 d Co Fe Mn - Forsiden · Anti-ferro magnetism B Anti ferromagnetism occurs in...
Kap
. 12
Mag
netic
solid
s
Wha
tW
hat
is
is m
agne
tism
mag
neti
sm??
Wha
tW
hat
is
is m
agne
tism
mag
neti
sm??
http
://w
ww
.uky
.edu
/~ho
ller/
orbi
tals
/
dd xyxy
dd yzyz
dd xzxz
nn
σσ∗∗
∆∆00
dd xx22 -- yy
22
dd zz22
FeCoNi
CrMn
Wha
tW
hat
is
is m
agne
tism
mag
neti
sm??
Dia
mag
neti
smD
iam
agne
tism
B
Dia
mag
netis
moc
curs
in m
ater
ials
with
noun
paire
del
ectro
ns. A
l 2O3,
MgO
etc
.
Par
amag
neti
smP
aram
agne
tism
B
Par
amag
netis
moc
curs
in m
ater
ials
with
unpa
ired
elec
trons
buti
nsuf
ficie
ntlo
ngra
nge
inte
ract
ion
betw
een
thei
rmag
netic
mom
ent.
Typi
calp
heno
men
aat
hig
hte
mpe
ratu
res.
Ferr
omag
neti
smFe
rrom
agne
tism
B
Ferro
mag
netis
moc
curs
in m
ater
ials
that
has
an e
xcha
nge
mec
hani
smw
hich
ensu
res
para
llelo
rient
atio
nbe
twee
nth
em
agne
ticm
omen
ts.
Ferr
iFe
rri
mag
neti
smm
agne
tism
BB
Ferr
imag
netis
moc
curs
in m
ater
ials
that
has
an
exch
ange
mec
hani
sm w
hich
en
sure
s a
net o
rient
atio
n be
twee
n th
e m
agne
tic m
omen
ts.
Ant
iA
nti --
ferr
ofe
rro
mag
neti
smm
agne
tism
B
Ant
i fer
rom
agne
tism
occ
urs
in m
ater
ials
that
has
an
exch
ange
mec
hani
sm w
hich
en
sure
s an
ti-pa
ralle
l orie
ntat
ion
betw
een
the
mag
netic
mom
ents
.
ΗΗΗΗ
ΜΜ
Μ =
Μ
= χχ
xx ΗΗ
Mag
netic
Mag
netic
susc
eptib
ility
susc
eptib
ility
χχ<
0 :
<
0 :
Dia
mag
netic
Dia
mag
netic
0 <
0 <
χχ<
1 :
<
1 :
Par
amag
netic
Para
mag
netic
χχ>
1 :
>
1 :
Fer
rom
agne
ticFe
rrom
agne
tic
Wha
tW
hat
to
to m
easu
rem
easu
re??
Wha
tW
hat
to
to m
easu
rem
easu
re??
Paramagnetic
Ferromagnetic
Antiferromagnetic
Ferrimagnetic
TC=
χθ
−=
χTC
θ−
=χ
TC
θ−ξ
+χ
+=
χT
CT01
1HH
MMSaturation
Saturation(M(M
ss))Remanence
Remanence(( MM
rr))
Coercivity
Coercivity(( HHcc))
Wha
tW
hat
to
to m
easu
rem
easu
re??
Wha
tW
hat t
o to m
easu
rem
easu
re??
Hard
Hard
HH
MMSoft
Soft
HH
MM
Easy
to
mag
netiz
e an
d de
mag
netiz
eM
inim
al r
eman
ence
Low
coe
rciv
ity
Har
d to
to
mag
netiz
e an
d de
mag
netiz
eVe
ry la
rge
rem
anen
ceCa
n be
mad
e in
to p
erm
anen
t m
agne
rts
Hig
h co
erci
vity
Wha
tW
hat
to
to m
easu
rem
easu
re??
Wea
kW
eak
mag
neit
cm
agne
itc
mat
eria
lsm
ater
ials
Diamagneticmaterials
: No
mag
netic
dipo
les
in th
em
ater
ial.
The
mat
eria
l res
pond
sto
ext
erna
lmag
netic
field
sac
cord
ing
to L
enz’
sLa
w.
Paramagneticmaterials
: The
mag
netic
mom
ent o
fthe
mat
eria
l is
depe
nden
t on
the
quan
tunm
num
bers
S, L
, J. T
hem
agne
ticm
omen
t for
tra
nsiti
onm
ater
islc
anbe
app
roxi
mat
edby
its
spin
-onl
yan
gula
rm
omen
ta:
()
[]
BJ
SS
gm
µ+
=21
1w
here
: g J
= 2
S =
num
bero
funp
aire
del
ectro
ns*
½µ B
= B
ohr m
agne
tron,
mag
netic
mom
ent o
fone
elec
tron
Ferr
omag
neti
cFe
rrom
agne
tic
mat
eria
lsm
ater
ials
Ferro
mag
netic
mat
eria
ls a
recl
aim
edto
hav
e an
inte
rnal
mag
netic
field
.
Ferr
omag
neti
cFe
rrom
agne
tic
mat
eria
ls, E
xcha
nge
mat
eria
ls, E
xcha
nge
ener
gyen
ergy
Che
mic
albo
ndin
gfa
vour
spa
iring
ofel
ectro
ns, g
ivin
gno
mag
netic
mom
ent.
The
exch
ange
ener
gy, j
, fav
ours
para
llels
pin
as fa
r apa
rtas
po
ssib
le. -
> H
unds
rule
Ferro
mag
netic
mat
eria
ls c
anbe
ob
tain
edw
hen
the
elec
trons
are
so
far a
part
that
they
can
be p
aral
lel
(viz
. a w
eak
bond
), bu
tstil
l so
clos
eth
atth
eyca
nin
tera
ctm
agne
tical
ly.
This
give
sin
gen
eral
wea
kbo
ndin
g.
Sof
t an
d ha
rd m
agne
tsS
oft
and
hard
mag
nets
Eas
yE
asy
and
hard
an
d ha
rd a
xis
axis
Ant
iA
nti --
ferr
omag
neti
cfe
rrom
agne
tic
Sup
erex
chan
geS
uper
exch
ange
Sup
erex
chan
geoc
curs
whe
nan
inte
rmitt
ent a
tom
(Oxy
gen)
tra
nsfe
rs o
rbita
l inf
orm
atio
nso
that
the
met
allic
neig
hbou
rs m
ust
be a
nti-p
aral
leli
n or
bita
l mom
ent.
With
outt
his
exch
ange
the
mat
eria
l wou
ldbe
par
amag
netic
.
Typi
calm
echa
nism
for a
nti-f
erro
mag
netic
oxid
esw
ithN
aCl-
type
stru
ctur
e.
T Nin
crea
ses
with
cova
lenc
y: M
nO, F
eO, C
oO, N
iOan
d is
dep
ende
nt o
nor
bita
l ove
rlap,
viz
. M-O
-M a
ngle
Ferr
imag
neti
cFe
rrim
agne
tic
mat
eria
ls,
mat
eria
ls,
Dou
blee
xcha
nge
Dou
blee
xcha
nge
Dou
blee
xcha
nge
occu
rsw
hen
elec
trons
can
jum
p be
twee
nm
etal
atom
s us
ing
an in
term
edia
teox
ygen
as b
ridge
. Bot
hel
ectro
nsju
mp
sim
ulta
neou
sly.
Thi
spr
oduc
espa
ralle
lspi
non
the
met
alat
oms.
This
mec
hani
smis
freq
uent
in in
vers
e sp
inel
s(F
e 3O
4, (F
e3+ [F
e2+ F
e3+ ]O
4et
c.) g
ivin
gfe
rrim
agne
ticm
ater
ials
.
Dom
ains
Dom
ains
Ferro
mag
netic
mat
eria
l pro
duce
a m
icro
stru
ctur
eof
mag
netic
dom
ains
”Wei
ss d
omai
ns”.
Thes
ere
duce
the
redu
ceth
em
agne
tost
atic
ener
gy.
Blo
ch w
all
Dom
ains
Dom
ains
Pau
liP
auli
para
mag
neti
smpa
ram
agne
tism
Par
amag
netic
met
als
do n
ot s
how
a C
urie
Wei
ss re
latio
nshi
p.TC
=χ
FB
EN
20µ
µ=
χ
By
appl
ying
an e
xter
nalf
ield
the
dens
ityof
stat
esfo
r the
upan
d do
wn
spin
stat
essh
ifts
diffe
rent
ly.
The
suce
ptib
ility
beco
mes
depe
nden
t on
the
appl
ied
field
, but
not t
empe
ratu
re.
Sup
erpa
ram
agne
tism
Sup
erpa
ram
agne
tism
Whe
npa
rticl
esof
a m
agne
ticso
lid a
rebe
low
the
dom
ain
size
, th
eel
ectro
stat
icin
tera
ctio
nsdo
min
ate.
The
mag
netic
dipo
les
tend
to a
lign
para
llelt
o ea
chot
hera
nd a
sup
erpa
ram
agne
ticst
ate
resu
lts.
Dom
ain
clos
ure
in th
infil
ms
