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ION IMPLANTATION INFLUENCE ON SPIN
ARRANGEMENTS IN GARNETS
L. Uba, S. Uba
To cite this version:
L. Uba, S. Uba. ION IMPLANTATION INFLUENCE ON SPIN ARRANGEMENTS IN GARNETS.
Journal de Physique Colloques, 1985, 46 (C6), pp.C6-69-C6-73. �10.1051/jphyscol:1985611�.
�jpa-00224849�
JOURNAL DE PHYSIQUE
Colloque C6, suppl6ment au n09, Tome 46, septembre 1985 page C6-69
ION I M P L A N T A T I O N I N F L U E N C E O N S P I N A R R A N G E M E N T S IN G A R N E T S L. Uba and S. Uba
I n s t i t u t e o f Physics, Warsaw University Branch i n Biatystok, Lipowa 41, 15-424 Biatystok, Poland
RBsumB
-
De nouveaux exemples d ' o s c i l l a t i o n s e n f o n c t i o n d e l a temperature d a n s les e f f e t s Kerr p o l a i r e e t t r a n s v e r s e s u r descouches minces d e g r e n a t i m p l a n t s e s ~ + s o n t d & c r i t s . L 1 i m p l a n t a t i o n i n d u i t une p h a s e magnetique modulee s p a t i a l e m e n t . On o b s e r v e une t r a n s i t i o n d e p h a s e magngtique s o u s champ d e l a p h a s e modulee v e r s une p h a s e homogene.
A b s t r a c t
-
Nevd examples of m a g n e t o o p t i c a l p o l a r and t r a n s v e r s e [ < e r r e f % e c t o s c i l l a t i o n s v s t e m p e r a t u r e i n 'H i m p l a n t e d t h i n g a r n e t f i l m s a r e r e p o r t e d . It i s proposed t h a t t h e i m p l a n t a t i o n i n d u c e s a s p a t i a l l y modulated m a g n e t i c phase. The f i e l d - i n d u c e d m a g n e t i c p h a s e t r a n s i t i o n from modulated p h a s e t o honogeneousi s o b s e r v e d .
I
-
INTRODUCTIONI o n i m p l a n t a t i o n i n f l u e n c e on m a g n e t i c p r o p e r t i e s of t h i n g a r n e t f i l m s have been i n v e s t i g a t e d p r e v i o u s l y by s e v e r a l methods /I/. However, be- c a u s e of t h e v e r y s m a l l t h i c k n e s s of sub-micrometer i m p l a n t a t i o n l a y e r s , t h e i n f o r m a t i o n d e r i v e d by most methods ( e x c l u d i n g CEMS / 2 / ) was a v e r a g e d o v e r t h e h i g h l y nonuniform i m p l a n t a t i o n p r o f i l e /3/. T h i s l e a d t o t h e d i f f e r e n t r e s u l t s o b t a i n e d by d i f f e r e n t methods. Such was t h e c a s e of i m p l a n t a t i o n i n d u c e d Nkel t e m p e r a t u r e s u p p r e s s i o n and a p p e a r a n c e of t h e p a r a m a g n e t i c p h a s e f o r l a r g e i m p l a n t a t i o n d o s e s
/2,4/. On t h e o t h e r hand, u n u s u a l g i a n t o s c i l l a t i o n s v s t e m p e r a t u r e of t h e m a g n e t o o p t i c a l p o l a r K e r r e f f e c t i n lie' i m p l a n t e d g a r n e t f i l m s have been r e c e n t l y r e v e a l e d /5/. Because of t h e s m a i l p e n e t r a t i o n d e p t h of t h e UV l i g h t i n t h e Kerr e f f e c t ( w 1 0 0
8.
) and c o n s i d e r a b l em a g n e t i c f i e l d i n f l u e n c e on t h e s h a p e of t h e s e o s c i l l a t i o n s i t h a s been s u g g e s t e d t h a t t h e n o n c o l l i n e a r s p i n a r r a n g e m e n t i s i n d u c e d by t h e i m p l a n t a t i o n /6/. I n t h e p r e s e n t worlc a new example o f t h i s phe- nomenon i n H+ i m p l a n t e d g a r n e t f i l m s , o b s e r v e d i n t h e p o l a r and t r a n - s v e r s e [ < e r r e f f e c t s , i s r e p o r t e d . It i s p r o p o s e d t h a t t h e i m p l a n t a - t i o n s c a n i n d u c e a s p a t i a l l y modulated s p i r a l o r s i n u s o i d a l magne- t i c phase. The f i e l d - i n d u c e d m a g n e t i c p h a s e t r a n s i t i o n from t h e modu- l a c e d t o t h e homogeneous p h a s e i s r e v e a l e d .
I n t h e p o l a r [ < e r r e f f e c t t h e sample was magnetized n o r m a l l y t o i t s
s u r f a c e and t h i s r e s u l t e d i n r o t a t i o n 9 of t h e p o l a r i z a t i o z p l a n e of t h e l i g h t r e f l e c t e d q u a s i n o r m a l l y ( a n g l e of i n c i d e n c e - 4 ) from t h e s u r f a c e . I n t h e t r a n s v e r s e ( o r e q u a t o r i a l ) Kerr e f f e c t /7/ t h e a.c, m a g n e t i c f i e l d i s a p p l i e d i n t h e s a m p l e p l a n e p e r p e n d i c u l a r l y t o t h e p l a n e of i n c i d e n c e of l i g h t . The l i g h t i s p o l a r i z e d i n i t s p l a n e of i n c i d e n c e and t h e a n g l e of i n c i d e n c e i s 6 g 0 , n e a r t o t h e B r e w s t e r
JOURNAL DE PHYSIQUE
'5'1
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a n s l e f o r t h e a a r n e t s . The r e - s u i t i n g m o d u l a t i o n of t h e r e f l e - c t e d l i g h t i n t e n s i t y A I =em>* I (H)
-
I(-H) g i v e s t h e magnitudeof t h e t r a n s v e r s e K e r r e f f e c t
6 =
AI/I. 3 0 t h e f f e c t s were mea- s u r e d by t h e e x p e r i m e n t a l s e t - u p.I) w i t h computer c o n t r o l l e d tempe-
d
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r a t u r e , f i e l d a n d s i g n a l proce- s s i n g /5/, The w a v e l e n g t h s of t h e l i g h t a s s u r i n g b o t h measura-unimplanttd
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l i g h t p e n e t r a t i o n d e p t h were bLe s i g n a l magnitude and s m a l l.
X )*
Ht/etn2 / 750 kcV-
c h o s e n ( A =314 nm i n t h e p o l a r0 10* ~ ' / c r n ~ / 150 keV and h = 4 0 5 nm i n t h e t r a n s v e r s e
a i O " ~ o * / c r n ' / ~ l ~ k o ~
-
[ ( e r r e f f e c t ) . E L l i p s o m e t r i c mea- s u r e m o n t s f o r t h e i m p l a n t e d g a r - n e t s have been done and d i e l e c -1 I I 1
-
t r i c c o n s t a n t components &,, and
750
H*[o~]
6, and hence r e f r a c t i v e i n d i c e sn and e x t i n c t i o n c o e f f i c i e n t s I<
have been o b t a i n e d /Uba and Uba, F i g . 1. P o l a r Kerr r o t a t i o n a s a t o be published/. G e n e r a l l y , i n
H~ i n p l a n t e d and o u r i n p l a n t e d g a r n e t s some than.. u n i m p l a n t e d s a m p l e s a t 235 K. cles i n n and I: a r e s e e n . The ca-
i c u l a t e d l i g h t p e n e t r a t i o n de- p t h s d -- %/8VI: a r e w i t h i n 150- 4 5 0
A
f o r 303-405 nm l i g h t used. Two i m p l a n t a t i o n s w i t h hydrogenH' i o n s 4 f f +150 I:eV e n e r g y and dog; $0 H /cm2
-
sample 1 and1 0 H /cm2
-
sample 2 were i n v e - st i g a t ed. The s a m p l e s were( Y S ~ C ~ ) ~ ( F ~ G ~ \ J ) Oq t h i n f i l m s ( a
few pn) grown
t y
LPE method on (111) p l a n e of GGG s u b s t r a t e ./-
-
A
-
111-
ZLSULTS AND DISCUSSION2
-
The measured t e m p e r a t u r e and"0-0 0 - e f i e l d d e p e n d e n c e s of t h e p o l a r
I),,-~-- and t r a n s v e r s e [ < e r r e f f e c t s re-
,
.'
f
/P
r o " H ~ ' / c ~ ' / IOOkeV-
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t ~ " ~ * / c m ' 1 i S k c V-
f l c c t t h e t e m p e r a t u r e and f i e l d b e h a v i o u r of t h e m a g n e t o o p t i c s - I l y - e f f e c t i v e m a g n e t i z a t i o n s of t h e g a r n e t /5,0/. F i g . 1 shows t y p i c a l f i e l d d e p e n d e n c e s of 8 H ) ICerr r o t a t i o n f o r s a m p l e s0
I I 1500
1000
HJo~] 'A FI d o s e s and f o r t h e sample ofI
i m p l a n t e d a t two d i f f e r e n t10j5 I-le+/100 I:eV i m p l a n t a t i o n . The s a t u r a t i o n p r o c e s s e s of t h e F i g . 2. T r a n s v e r s e Kerr e f f e c t a s K e r r r o t a t i o n s e e n i n F i g c 1 r e - a f u n c t i o n of I-1,) f o r i m p l a n t e d and f l e c t t h o f a c t t l ~ a t t h e m2gnet-i- u n i m p l a n t e d s a m p l e s a t 295 I<. z a t i o n i n t h e i m p l a n t e d g a r n e t s
under normal HI f i e l d r o t a t e s from t h e sample p l a n e t o t h e no- rmal d i r e c t i o n (bl~hich i s t h e e a s y d i r e c t l o n Ln t h e u n ~ m p l a n t e d sam- p l e ) . The s a t u r a t i o n f i e l d
increases
s t r o n g l y w i t h t h e d o s e of t h eH+ i m p l a n t a t i o n and f o r t h e ~ e + i m p l a n t a t i o n i s g r e a t e r t h a n f o r t h e
H+ i m p l a n t a t i o n of t h e same dose. The s a t u r a t i o n f i e l d
~ i &
i s a mea- s u r e of t h e e f f e c t i v e a n i s o t r o p y f i e l d H K =-
471 f ; , i n d u c e d by i m -F i g . 3. T e m p e r a t u r e d e p e n d e n c e s of p l a n t a t i o n i n t o t h e g a r n e t t h e p o l a r Merr r o t a t i o n f o r unimpla- f i l m v i a p e r p e n d i c u l a r l a t - n t e d (a) and i m p l a n t e d 10" !-I+/ t i c e s t r a i n and n e g a t i v e 1 5 0 keV s a m p l e s a t HL= 250 Oe (o)and m a g n e t o s t r i c t i o n /I/. The 111= 6 !c~e(m). a b o v e H : ~ ~ d o s e and implan-
t e d i o n t y p e d e p e n d e n c e s a r e c o n s i s t e n t w i t h t h e r e s u l t s o b t a i n e d by o t h e r methods /1,8,9/. F i g . 2 shows t y p i c a l f i e l d d e p e n d e n c e s of t h e t r a n s v e r s e K e r r e f f e c t
for
t h e same samples. Q u i t e an o p p o s i t e f i e l d b e h a v i o u r of t h e n a g n e t i z a - t i o n i n c o n p a r i s o n w i t h t h e c a s e of p o l a r [ < e r r e f f e c t c a n be d e r i v e d from F i g . 2. To r o t a t e m a g n e t i z a t i o n i n t h e u n i m p l a n t e d s a n p l e from normal t o t h e sample p l a n e a l a r g e f i e l d 11, i s needed, The magnetima- t i o n i n t h e 1 0 ~ ~ t . 1 ~ / 1 5 0 !ceV i m p l a n t e d sample i s l i k e l y t o be d i r e c t e d under s m a l l a n g l e t o tl e normal. T h i s i s c o n c l u d e d from t i l e f a c t t h a t q u i t e a l a r g e f i e l d Hf?' iiss t o be used t o Cet t h e t r a n s v e r s$
! < e r r e f f e c t s a t u r a t i o n . Thel-l;Ft
i n t h e 1 0 ~ ~ t 1 + / 1 5 0 !;eV andl o d 5
11e / I 0 0 lceV s a m p l e s a r e much s m a l l e r i n d i c a t i n g a s m a l l a n g l e between t h e magno- t i z a t i o n d i r e c t i o n and t h e s a n p l e p l a n c . The t r a n s v e r s e and p o l a r I:err e f f e c t r e s u l t s a r e t h e n c o n s i s t e n t and supplement e a c h o t h e r . Both e f f e c t s can s e r v e a s a method of measurement of a n i s o t r o p y f i e - l d s i n v e r y t h i n s u r f a c e L a y e r s of m a g n e t i c m a t e r i a l s ,I n t h e H+ i m p l a n t e d g a r n e t s t e m p e r a t u r e measurements of I:err r o t a t i o n r e v e a l o s c i l l a t o r y b e h a v i o u r , f i r s t o b s e r v e d f o r t h e He* i m p l a n t a t i o n
/5 G/. I n F i g s . 3 and 4 we s h o v ~ @ ( T ) measured i n i m p l a n t e d g a r n e t s a t
~ : b t
( s e e F i g . 1 ) and a tI-:I=
6 I:Oe >>t-Iiot.
For comparison B(T) f o rt h e u n i m p l a n t e d p a r t of t h e sample i s shown t h e r e t o o . I t 5 s s e e n t h a t s t a r t i n g from TN t h e t e m p e r a t u r e r a n g e of oscillations e x p a n d s t o l o w e r t e m p e r a t u r e s w i t h t h e i n c r e a s e of t h e :iC d o s e a t c o n s t a n t e n e r g y ( ~ i g s . 3 and 4 ) . For s m a l l d o s e 1 0 ~ ~ 1 - l + / c r n ~ t h e o s c i l l a t i o n s
C6-72 JOURNAL DE PHYSIQUE a r e s o weak t h a t i n t h e s t r o n g f i e l d u s e d t h e y n e a r l y d i s a p p e a r F o r g r e a t e r d o s e 1 0 ' ~ ~ + / c m ~ a w e a k e r f i e l d i n f l u e n c e i s o b s e r v e d . S i m i l a r be- h a v i o u r f o r lle+ i n p l a n - t a t i o n a t c o n s 2 a n t d o s e
l o 4 =
tle+/cn2 a n d i n c r e a - s e d e n e r g y w a s o b s e r v e d /G/. I t c a n b e r e m e r k e d t h a t a l t h o u g h p a r a m e t e r s 1 0 ' ~ ~ ~ / 1 5 0 keV a n d 10 " ~ e + / 1 0 0 keV e r e si- m i l a r t h e tleC i m p l a n t a - t i o n i n d u c e s much s t r o n - g e r o s c i l l a t i o n s t h a n H' i m p l a n t a t i o n d o e s . T h i s c a n b e c o n n e c t e d n i t h t h e d i f f e r e n c e s i n 2r.1- p l a n t a t i o n i n d u c e d c h e n - g e s i n t h e g a r n e t , d u e t o d i f f e r e n t i m p l a n t e d i o n s . T h e s e d i f f e r e n c e s F i g . 5. T e m p e r a t u r e d e p e n d e n c e s o f t h e a r e r e f l e c t e d by t h e ma- t r a n s v e r s e ICerr e f f e c t f o r 1 0 ~ ~ ~ + / 1 5 0 I:eV g n i t u d e O f t h e observed a t NII = 5 0 0 O e ( o ) a n d 10461++/150 1:eV i n - K e r r r o t a t i o n which de- p l a n t e d s a m p l e a t ll,,=1300 Oe ( 0 ) . c r e a s e s n i t h t h e i n c r e a - s e o f t h e i m p l a n t a t i o n d o s e a n d e n e r g y , a s r v e l l a s by t h e E d e l t e m p e r a t u r e s u p p r e s s i o n ( o b - s e r v e d i n /5,6/ a n d i n F i g s . 3 a n d 4 ). I t i s t o b e n o F i c e d t h a t , de-spite
d i f f e r e n t d i r e c t i o n o f t h e a p p l i e d f i e l d ,s i m ~ l a r
b e h a v i o - u r o f t h e t r a n s v e r s e K e r r e f f e c t v e r s u s t e m p c r a t u r e ( a n d v s i n - p l a n e m a g n e t i c f i e l d ) h a s b e e n o b s e r v e d . I n F i g . 5 we s e e e x a m p l e s o f d ( ~ ) d e p e n d e n c e s o b t a i n e d a t s a t u r a t i o n!iYt
f i e l d s f o r s a m p l e 1 a n d 2. Q u a n t i t a t i v e c o m p a r i s ~ o n o f t h e p o l a r a n d t r a n s v e r s e K e r r e f f e c t s i n s u c h a n d o t h e r c a s e s m i l l b e p u b l i s h e d e l s e w h e r e . C o n c l u d i n g , we s u - g g e s t t h a t t h e i m p l a n t a t i o n d a m a g e , s t r a i n ( l o w e r i n g o f t h e c r y s t a l s y m n e t r y ) a n d s u p e r e x c h a n g e r e d u c t i o n i n d u c e s a new m a g n e t i c p h a s e . T h i s p h a s e a p p e a r s a b o v e c e r t a i n t e m p e r a t u r e w h i c l i g r o w s w i t h t h e c r o v ~ t h o f t h e m a g n i t u d e o f t h e c h a n g e s t h e i m p l a n t a t i o n i n d u c e s i n;he garnet r61. For weak implantations and weal; c r y s t a l c h a n g e s t h i s new p h a s e ( v ~ h i c h c a n b e c a l l e d m o d u l a t e d o r i n c o m m e n s u r a t e p h a s e a s i n t h e c a s e o f h e l i m a g n e t i s m i n h e a v y r a r e e a r t h m e t a l s / l o / ) c a n b e n e a r l y c o m p l e t e l y r e d u c e d t o h o m o g e n e o u s i n t h e n a g n e t i c f i e l d s o f t h e o r d e r o f 6 kOe. I n i m p l a n t e d g a r n e t s t h e s i n u s o i d a l o r s p i r a l d i s t r i b u t i o n o f t h e m a g n e t i z a t i o n a n d i t s p o s s i b l e c h a n g e w i 2 h tem- p e r a t u r e a n d f i e l d c o u l d b e o b s e r v e d w i t h i n t h e l i g h t p e n e t r a t i o n d e p t h . F o r s t r o n g e r i n p l a n t a t i o n s a s t r o n g e r m o d u l a t e d p h a s e a p p e a r s a n d a g r e a t e r m a g n e t i c f i e l d h a s t o b e u s e d t o t u r n t h e p h a s e b a c k t o h o m o g e n e o u s . F u r t h e r e x p e r i m e n t s i n l a r g e r m a g n e t i c f i e l d s a s w e l l a s t h e o r e t i c a l d e v e l o p m e n t s o f t h e a d e q u a t e m o d e l s a r e p l a n n e d . T h e a u t h o r s w i s h t o a c l : n o \ v l e d g e t h e many s t i m u l a t i n g d i s c u s s i o n s w i t h P r o f e s s o r N.Szymczak. T h a n k s a r e d u e t o P r o f e s s o r ~ . S n i e c l c i a n d D r . /\.Claziev!s!:i f o r c r i t i c a l r e a d i n g o f t h e m a n u s c r i p t a n d Mr. A.
Dgb!;owski For p r e p a r a t i o n of s a n p l e s . T h i s n c r k was s u p p o r t e d i n p a r t by I n s t i t u t e o f P i i y s i c s , P o l i s f i Academy of S c i e n c e s , blarsaci.
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/I,/ G e r a r d , P., T h i n S o l i d F i l m s
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(1984) no, 1/2.,/2/ P i c o n e , P.J. a n d l . i o r r i s l i , t2.1-:., ?./?.ppl.Phys. 5 3 ( 1 9 ~ 2 ) 2471. /3/ I . i e t s u t e r a , H., Esho, S . anc! I-lidalca, Y., ~ . r i p ~ x ~ i l ~ s .
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4 l , i a a r t e n s e , I. a n d S e a r l e , C.i:.
,
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(1'380) 5919. /5/ Uba, L. a n d Uba, S., 2-nd I n t e r n a t i o n a l C o n f e r e n c e on P h y s i c s ofl l a g n e t i c G i a ? e r i a i s , S e p t e m b e r 13Z.4, J a d n i s i n , P o l a n d , i n : Acts P h y s i c a P o l o n i c a ( 1 9 8 5 ) .
/ 6 / Uba, L. a n d Uba, S., S o l i d S t a t e Commun. ( 1 9 8 5 )
/7/ Lee, E.!'!,
,
C a l l a b y , D.R. a n d Lynch, A.C., P r o c . Phys. Soc. LXXII 2 ( 1 3 5 8 ) 233./ 8 /
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