Gorodetsky, G

Rozenberg, E

Shames, A I

IACS Institutional Repository

Indian J. Phys. 75A (4), 313-316 (2001)U P  Aan international journalElectron magnetic resonance in doped colossal magnetoresistive manganitesA 1 S h a m e s , E  R o z c n b c r |*  a n d  G  G o ro d e ts k yDepartment of Physics, Ben-Gunon IJmvirsiiy of the Negev POB 653, 84105.Bccr-Shevaj IsraelW  H M c C ^ rro llChemistry Department, Ruler University, 2083 Lawrcnceville Road.I-awrenceville. 08854. USAa n dM  G rc e n b la t tDepartment of Chemistry, Rutgers University. Piscataway,New Jersey 08854-8087. USAE-mail evgenyrCo'bgumail bgu.ac.ilXhstract The experimental results of electron magnetic resonance study on powdered ceramics samples of LaMn-perovskiies doped by divalentrh. Sn and Zn ions, as well as those for powdered single crystals doped by Na are presented The main and common features observed for the resonant l^H.\^ ra of all the sattiples could be noted . a) gradual change of the broad asymmetric line of ferromagnetic resonance (FMR) to narrow line of electron paramagnetic resonance (EPR) with temperature T; h) coexistence within certain temperature inicrvals of FMR and EPR signals, as well as the signals M F-MR and ferromagnetic anliresonancc ; c) minimum of the linewidth in the vicinity of I 1 T and its linear broadening above this temperature; d) vlouble integrated intensity of the signal obeys Arrhenius law above I 1 T . e) specific effect of the non-resonant surface microwave absorption The tcsulis obiained for poly- and singlC'Crysiallinc samples are compared The disputable problems in this field are noted.Keywords : Ferromagnetic resonance, electron paramagnetic resonance. Mixed-valence doped manganitesI’ACS Nos, . 76.50.4-g. 76.30 Fc1. IntroductionThe p e ro v sk ite  m a n g a n i te s  o f  th e  fo rm  ( L a j ^ A j M o O ^ ,  w h e re  A IS a d iv a le n t io n  s u c h  a s  C a , S r, B a  e tc . ,  h a v e  b e c o m e  re c e n tly  fa sc in a tin g  s y s te m  f o r  r e s e a r c h e r s  d u e  to  v a r ie ty  o f  th e ir  n ia g n c tic  a n d  c o n d u c t i v e  p r o p c r l i e s f  1 -4 ] . T h e  u n d o p e d  sto ich iom etric  (x  =  0 )  L a M n O ^  c o n ta in s  o n ly  io n s  a n d  is classified a s  c a n te d  a n l i f e r r o m a g n e l  (A F ) . T h e  s u b s t i tu t io n  o f  by d iv a le n t  A ^^ io n s  r e s u lts  in  a  m ix e d  v a le n c y  o f  Mn^"^ and M n"^ io n s  a n d  a  v a r ie ty  o f  e le c tro n ic  a n d  m a g n e t ic  p h a se s , fhc fe r ro m a g n e t ic  ( F M )  o r d e r in g  is  g o v e r n e d  m o s tly  b y  a  x louble-cxchange (D E )  in te ra c t io n  ~  Mn'*^. In  m o s td o p ed  m a n g a n i te s ,  a  t r a n s i t io n  f ro m  a  m e ta ll ic  F M  to  a  param agnetic  s e m ic o n d u c to r - l ik e  p h a s e  o c c u rs  a t  a  te m p e ra tu re  h e a tin g . T h is  tr a n s i t io n  m a n ife s ts  i t s e l f  b y  a  m a x im u m  Piw(7') in  th e  r e s i s t iv i ty .  A  s p e c i a l  a t t e n t io n  is  a d d r e s s e d  'c o lo s s a l  m a g n e t o r e s i s t a n c e "  ( C M R )  e f f e c t  in  th e s e  co m p o u n d s, b e in g  a  h u g e  ( u p  to  th o u s a n d f o ld )  c h a n g e  in^«>rrcspDnding A uthorre s is tiv ity  u n d e r  an  e x te rn a l m a g n e tic  f ie ld , in  th e  v ic in ity  o f  th e  C u rie  p o in t T^ ,.E le c t r o n  m a g n e t ic  r e s o n a n c e  (E M R ) ,  n a m e ly , e le c t r o n  p a ra m a g n e tic  re s o n a n c e  (E P R )  a t T > T  a n d  fe r ro m a g n e t ic  re so n an ce  (F M R ) a t 7 <  T , is a  u sefu l too l fo r s tu d y in g  a  m ag n e tic  s t r u c tu r e  a n d  its  c h a n g e  u n d e r  th e  in f lu e n c e  o f  e x te r n a l  p a ra m e te r s  (m a g n e tic  f ie ld  H , te m p e ra tu re  T, e tc .) . T h e  u se  o f  E M R  te c h n iq u e  fo r  s tu d y in g  th e  p e ro v s k ite  m a n g a n i te s  s ta r ts  f ro m  1969^ a n d  is  in te n s iv e ly  d e v e lo p e d  d u r in g  la s t y e a rs  (s e e  fo r  e x a m p le  (3 ,6 ,7 ]  a n d  r e fe re n c e s  th e re in ) . T h e  c u r r e n t  p a p e r  p re s e n ts  th e  b r ie f  re v ie w  o f  th e  re c e n t  re s u lts  o f  E M R  s tu d ie s  o f  d o p e d  L a -p e ro v s k ile  m a n g a n i te s  o b ta in e d  in  th e  L a b o ra to ry  o f  M a g n e t ic  R e s o n a n c e  o f  B e n -G u r io n  U n iv e rs i ty  o f  th e  N e g e v . T h e  re s u lts ,  p re s e n te d  in  th e  S e c tio n  2 , a re  fo c u s e d  o n  s tu d ie s  o f  P b , S n  a n d  Z n - d o p e d  p o ly c r y s ia l l in c  L a M n -p e r o v s k i te s .  S e c t io n  3 c o n ta in s  d a ta  o n  E M R  p r o p e r t i e s  o f  g r o u n d e d  (p o w d e re d )  s in g le -c ry s ta l l in e  ^jg^Na^, i3M n^^g ^ 0 3  s a m p le s . D is c u s s io n  a n d  c o n c lu s io n s  a re  in  S e c tio n  4 .©2001 LAGS314 A I Shames, E Rozenberg, G Gorodetsky, W H McCarroll and M Greenhlatt2. Experimental details and resultsE M R  m e a s u re m e n ts  o n  p o w d e r  sa m p le s  in  th e  te m p e ra tu re  ra n g e  1 0 0  (±  0 .5 )  <T<  4 2 0  (±  0 .5 )  K  w e re  c a r r ie d  o u t u s in g  B ru k e r  E M X -2 2 0  d ig ita l X -b an d  (9 .4 0  G H z ) sp ec tro m e te r an d  E R  4 1 2 1 V T  te m p e ra tu re  c o n tr o l le r  ( fo r  Z n -  a n d  N a -d o p e d  sa m p le s  th e  a b o v e  in te rv a l w a s  e x te n d e d  d o w n  to  4 .2  K ). T h e  p ro c e s s in g  o f  th e  s p e c tra  w a s  p e r f o rm e d  b y  B ru k e r  W IN -E P R  S o f tw a re . In  o rd e r  to  e lim in a te  s iz e  e f f e c ts  a n d  c a v ity  o v e r lo a d in g , p o w d e r  sa m p le s  o f  s e v e ra l m g  w e re  p la c e d  a t th e  b o tto m  o f  1 -m m  g la s s  c a p il la ry  tu b e s  c e n te re d  in  th e  r e c ta n g u la r  cav ity . T lic  m e a s u re m e n ts  w e re  d o n e  in  th e  l in e a r  r e s p o n s e  re g im e  a t m ic ro w a v e  p o w e r  2(X) |LiW. In  c o n t r a s t  to  th e  r e s u l t s  o b ta in e d  b y  S c e h ra  et a! [ 8 ], n o  a s y m m e tr ic  ( D y s o n ia n - l ik e )  l in e -s h a p e s  w e re  o b se rv e d  in  th e  p a ra m a g n e tic  re g io n , w h ic h  a l lo w e d  u s to  w o rk  w ith o u t an y  d i lu t io n  o f  sa m p le s .T h e  p o ly c r y s ta l l in e  P b , S n  a n d  Z n -d o p e d  m a n g a n i te s  w e re  o b ta in e d  b y  s ta n d a rd  c e ra m ic  te c h n o lo g y  (s e e , fo r  in s ta n c e ,[ 9 ] ) .  T h e  C u r ie  t e m p e r a t u r e s  f o r  L a ,^ ^ Z n ^ M n 0 3  s a m p le s ,  o b ta in e d  b y  s u s c e p tib i l i ty  m e a s u re m e n ts ,  w e re  fo u n d  a s  =  180 K ; 16 0  K ; 150 K  a n d  125 K  (w ith in  th e  e x p e r im e n ta l e r ro r  o f  ±  2 K ) fo r X =  0 .0 5 ; 0 .1 ; 0 .2  a n d  0 .3  c o rre sp o n d in g ly . IT ic p ro c e d u re  o f  g r o w th  o f  s i n g l e - c r y s t a l l i n e  s a m p le s  o f984^3 fu s c d -s a l t  e le c t ro ly s is  is  p re s e n te d  in  1 1 0 ], T  w as  fo u n d  to  b e  3 0 0  K .150IflCIT V210 K| 2051^200 K 195 K J90K J85IC  J80IC  J 7 5 K  170K600150 300 450Magnetic Field H, (mT)F ig u r e  1 . Tem perature d ep en d en ce  o f  EM R  sp ectra  o f  p o ly cry sta llin e  L ap ^ Z n o^ M n O ,: (a) b elow  C urie temperature s i 8 0  K, veirtical arrows point the position o f  ferrom agnetic antiresonance signal ; (b) c lo se  to and above T .T h e  fo l lo w in g  m a in  a n d  c o m m o n  fe a tu re s  o f  E M R  spectra ( th e  ty p ic a l  g r a p h s  a r e  p r e s e n te d  f o r  Z n - d o p e d  powdered  m a n g a n i te s )  w e re  o b s e rv e d  in  p o ly c r y s ta l l in c  s a m p le s  [9 , i ] j(i) A  ty p ic a l a s y m m e tr ic  b ro a d  F M R  s in g le  e x is ts  at T< T \[ c h a n g e s  g ra d u a lly , i.e., n a r ro w s  a n d  s h if ts  to  h ig h e r  H  w hen the e x te rn a l te m p e ra tu re  in c re a se s . A t a p p ro a c h in g  th e  F M R  suinal g ra d u a lly  tu rn s  to  th e  s y m m e tr ic  L o re n tz ia n  E P R  s ig n a l w hich is o b s e r v e d  a t 7  ^  1.1 7 .  ( F ig u r e  1). T h e  g - f a c to r  w ith in  the p a ra m a g n e tic  r e g io n  d e c re a s e s  f ro m  th e  v a lu e s  a b o v e  2  0  to 1.9 8 7  ±  0 .0 0 1 , w h ic h  is  c lo s e  to  th a t  o f  n o n -c o u p le d  M n ‘*^  ions( i i)  T h e  f e r r o m a g n e t ic  a n t i r e s o n a n c e  (F A R ) is  observed w ith in  .som e in te rv a l o f  te m p e ra tu re s  a t 7 <  7 .  It m a n ife s ts  nsd{ as  a  lo w -f ie ld  d ip  in  th e  F M R  sp e c tra . T h e  u n u su a l (n o t descnfx:tl b y  th e o ry  u s e d  in  [ 1 2 ])  te m p e ra tu re  d e p e n d e n c e  o f  th e  resonant fie ld  o f  F A R , e.g. its  sh if t to w a rd s  z e ro  fie ld  w h en  th e  tcm peratu ir a p p ro a c h e s  7 ^ , is  o b s e r v e d  (F ig u re  la ,  v e r t ic a l  a rro w s ) .(iii) W ith in  c e rta in  in te rv a l o f  te m p e ra tu re s  7 <  1 .1 7'^  a natmw E P R  s ig n a l c o e x is ts  w ith  a  b ro a d  F M R  o n e . T h e  a b o v e  signals m a y  b e  s u p e r im p o s e d  o n e  o n  a n o th e r  o r  n o ta b ly  sh if te d  imi H d e p e n d in g  on  th e  n a tu re  o f  d o p in g  io n , a s  w e ll as  on  crysi.il s tru c tu re  o f  th e  s a m p le  ( s in g le - o r  p o ly c r y s ta l l in e  o n e ).( i v )  T h e  l i n e w i d t h  o f  th e  EM R s ig n a l  has up r o n o u n c e d  m in im u m  in  th e  v i c in i t y  o f  7 - 1 .1 7 ^  At ilu te m p e ra tu re s  a b o v e  1. IT^, a n d  u p  to  a t  le a s t 2T^, th e  E P R  liiu b ro a d e n s  lin e a r ly  ( f ig u re  2 ).F ig u r e  2. Dependence of the EMR linewidth for polycryslalhm*La,^Zn_^MnO, samples vs. normalized temperature. The straight line describes a linear fit (the sam e for all sam ples) at T>  1.1 7 .(v )  T h e  n o rm a liz e d  d o u b le  in te g ra te d  in te n s i ty  (D I)  o f  the E P R  s ig n a ls  (F ig u re  3 a )  a re  w e ll  f i t te d  a t 7  >  1.1 7  by A rrh e n iu s  r e la t io n  o f  th e  fo rm  [ 1 3 ] :DI^l^cxpiAK/ksTl  (0w h e re ’ in  in te r p r e te d  a s  a  th e r m a l a c t iv a t io n  e n e rg y  fof d is s o c ia t io n  o f  sp in  c lu s te r s  (F ig u re  3 b ).(v i)  T h e  e f f e c t  o f  n o n - r e s o n a n t  s u r fa c e  m ic ro w a v e  absorpii^^ f i r s t  o b s e rv e d  o n  m a n g a n i te s  b y  L o f la n d  etal [6 ] fo r  IIE, wasElectron magnetic resonance in doped colossal magnetoresistive manganites 315jc tcc ted  fo r  th e  g e o m e try  f f l E  ty p ic a l  in  m a g n e t ic  re s o n a n c e  ex p erim en ts . T h is  e f f e c t  m a n i f e s t s  i t s e l f  b y  th e  n o n - t r iv ia l  tem perature d e p e n d e n c e  o f  d o u b le  in te g ra te d  re s o n a n c e  s ig n a l, having a  m a x im u m  a t T <  7^ (s e e , fo r  e x a m p le  R ef. [9] a n d  F ig u re3a).o r ie n ta t io n a F  a n d  te m p e ra tu re -d e p e n d e m  at 7 <  1.1 7 ’. (F ig u re s  4 c , d ). T o o u r  m in d , th e  a b o v e  n o te d  o s c i l la tio n s  re s u lt  fro m  su c h  s tru c tu re  th e  s p e c tra  o f  b u lk  s in g le -c ry s ta ls .Fij^urc 3. Temperature dependence of the intensity of EMR signal for polycryslalline sample ; (a) normalized doublemiegrated intensity (1)1) of the first dcnvativc signal ; (b) Arrhenius plot ‘<f 01 at temperature above T.3. Results for single-crystalline powdersThe g rea t a d v a n ta g e  o f  g ro u n d  s in g le -c r y s ta ls  a s  an  o b je c t fo r  E M R  s tu d y  is  t h e i r  c h e m ic a l  " s i n g l e - p h a s e ” s t a te  g iv in g  possibility fo r  m a n ife s ta tio n  o f  a d d it io n a l d e ta i ls  on  in v e s tig a te d  spectra. A t th e  sa m e  tim e , a ll th e  a b o v e  p e c u lia r itie s  o f  th e  sp ec tra  arc the in tr in s ic  o n e s , c h a ra c te r is tic  fo r  in v e s tig a te d  m a n g a n ite s . This su g g e s tio n  is  d ir e c t ly  c o n f i rm e d  b y  e x p e r im e n ta l d a ta , o b ta in e d  o n  p o w d e r e d  s i n g l e - c r y s t a l l i n e  s a m p l e s  o f^  887^^0 113 ^ ” 0.984®.VAll th e  r e g u la r i t ie s  ( i)  -  (v i)  d e s c r ib e d  in  S e c tio n  2 a rc  a ls o  ch arac teris tics  fo r  E M R  s p e c tr a  o f  th e s e  s a m p le s . A d d itio n a lly , te m p e ra tu re  in te rv a l  o f  th e  c o e x is te n c e  o f  F M R  a n d  E P R  i'ignals ( r e g u la r i ty  ( i i i ) )  is  e x te n d e d  upio A T  ^7 0  K. T h e  lin e s  are c lea rly  s e p a r a te d  (F ig u re  4 a ) . T h e  n e x t  im p o r ta n t  fe a tu re  o f  observed s p e c tra  is  th e  p re s e n c e  o f  n o is c - l ik e  o s c i l la tio n s  o n  EMR line , w h ile  th e  E P R  s ig n a l  o f  a b o u t  th e  s a m e  in te n s i ty  is  a  noiseless o n e . T h is  fe a tu re  m a y  b e  b e tte r  o b s e rv e d  in  th e  2 -n d  derivative s p e c tru m  a t  th e  s a m e  te m p e ra tu re  (F ig u re  4 b ). I t  is  im portant to  n o te  th a t th e  F M R  s p e c tra  o f  th e  b u lk  s in g le -c ry s ta ls  consist o f  s u p e r p o s i t io n  o f  m u l t ip le  s h a r p  l in e s , w h ic h  a re  b o thFigure 4. EMR spectra of samples at 7'^  290 K : (a)first derivative EMR spectrum of polycryslalline sample . (b) second derivative EMR spectrum of polycrystalline sample at higher receiver gain ; (c) first derivative EMR spectrum of single-crystalline sample, H lk()0l>, (d) first derivative EMR spectrum of single-crystalline sample, H lkOIO>4. Discussion and conclusionsT h e  m a in  re s u lt o f  o u r  E M R  in v e s t ig a t io n  is th e  p re s e n c e  o f  in trin sic  m a g n e tic  in h o m o g c n c itic s  in  a ll o f  th e  m a n g a n ite s  u n d e r c o n s id e ra t io n . A t 7 >  7^ in h o m o g e n e it ie s  (v a r io u s  m a g n e tic a l ly  o rd e re d  s u b s y s te m s )  m a n ife s t  i t s e l f  a s  sh o r t- r a n g e  F M  o rd e re d  e n ti t ie s  d is s o c ia t in g  w ith  T  a c c o rd in g  to  th e  A rrh e n iu s  L a w  eq .(1 ). M o re o v e r, m a g n e tic  in h o m o g c n c it ic s  a re  c le a r ly  d e te c te d  at 7 <  7  (see , for ex am p le . F ig u re  4 ), w h e re  p a ram ag n e tic  "dom ains" e x is t w ith in  F M  m a tr ix  a n d  c o n tr ib u te  a  n o ta b le  E P R  s ig n a l to  th e  re s u lta n t sp e c tra , l l i e  la s t o b s e rv a tio n  is s tro n g ly  c o n f irm e d  by  N M R  an d  E M R  d a ta  o f  [ 1 3 -1 6 |.S u rp ris in g ly , the  m a g n e tic  in h o m o g c n c itic s  a re  (in so m e  w ay) m o re  p ro n o u n c e d  in  s in g le -c ry s ta l l in e  s a m p le s . I t  re s u lts  in  the  e x te n d e d  te m p e ra tu re  in te rv a l o f  th e  c o e x is te n c e  o f  E P R  an d  F M R  sig n a ls . O n  th e  o th e r  h a n d , v e ry  c o m p le x  s tru c tu re  o f  F M R  s p e c t r a  o f  b u lk  s in g l e - c r y s t a l l i n e  s a m p le  ( a n d  n o is e - l ik e  o s c i l la tio n s  o n  sp e c tra  o f  p o w d e rs )  n o te d  in  S e c tio n  3 m a y  a lso  b e  c o n n e c te d  w ith  a fo re n a m e d  in h o m o g e n e it ie s . N a m e ly , th e  v o lu m e  o f  th e  b u lk  c ry s ta l m a y  c o n ta in  a n u m b e r  o f  re g io n s  w ith  d if fe re n t c o n s ta n ts  o f  m a g n e to c ry s la l l in c  a n iso tro p y , T ^s etc., c o n n e c te d  w ith  lo ca l s tru c tu ra l d e fe c ts  o r  n o n -s to ic h io m e try . U p  to  n ow , th e  d a ta  o n  res ^ n an l p ro p e r t ie s  o f  s in g le -c ry s ta ll in e  m a n g a n ite s  a re  n o t n u m e ro u s , b u t F M R  s p e c tru m  o f  P b -d o p e d  s a m p le  p re s e n te d  in  R e f . [1 2 ] c le a r ly  s h o w s  a  c o m p l ic a te d  s tru c tu re  s im ila r  to  th a t  n o te d  in  th is  p ap e r. In v e s tig a t io n s  o f  E M R  p ro p e r tie s  o f  s in g le  c ry s ta ls  a rc  n o w  in  p ro g re s s  a n d  th e  re s u lts  w ill b e  p u b lis h e d  e ls e w h e re .M e a s u r e m e n ts  o f  r e s o n a n t  p r o p e r t ie s  o f  s in g le  c r y s ta ls  d ir e c t ly  c o n f i rm  a ls o  o u r  in te rp re ta t io n  o f  th e  e f f e c t  o f  n o n -  re s o n a n t su r fa c e  m ic ro w a v e  a b so rp tio n  ( re g u la r ity  (v i)  in  S e c tio n316 A / Shames, E Rozenberg, G Gomdetsky, W H McCarroll and M Greenblatt2). Namely, the above effect (maximum in the temperature dependence of DI) is absent for the bulk samples with strongly reduced area of interfaces. The model of one phonon spin-lattice relaxation process [8] may explain the linear broadening of the linewidth (regularity (iv)) at paramagnetic temperatures. The minimum linewidth found at T -  I. I T may be associated with exchange narrowing as a consequence of enhanced double exchange within the cluster due to high localisation of the wave function of the change carriers [ 11 ]. At the same time, the reason for equal (within the experimental error) slope of lineardependence of A/f vs. normalized temperature TIT^  (sec Figure 2) observed for numerous different manganites at 7 >  1.1 isnot understood at the moment. The absence of the theoretical interpretation of the "universal "1.1 T. value could also be noted.AcknowledgmentsThe research was supported by the Israeli Science Foundation administered by the Israel Academy of Sciences and Humanities and the Israeli Ministry of Immigrant Absorption for the CAMEO fellowship (A. Sh. and E. R.). Authors thank Dr. B. Revzin for sintering of Zn-doped samples.References(1) A P Ramirez I  Ph\s. : Cond Matter, 9 8171 (1997)(2) Colossal Magnetoresistanve Charge Ordering and Related properties oj Manganese Oxides (cd) CNR Rao and B Raveau (Singapore ; World Scientific) p 345 (1998)(3] J M D Cocy, M Vircl and S von Molnar Adv Phys, 48 167 (I999,14] A J Minis Nature 392 147 (1998)[5] C W Cearle and S T Wang Canad J, Phys. 47 2703 (1969)[6 ] S E Lofland, P H Kim, P Dahiroct, S M Bhagat, S D Tyagi  ^Kwon, R Shreckala, R Ramesh and T Venkatesan J. Phys Cond Matter 9 m i  (1997)[7] M T Causa, M Tovar, A Caneiro, F Prado, G Ibanez, C A kanios A Butcra, B Alascio, X Obrados, S Pinol, F Rivadulla, C Va/que^  Vazquez, M A Lopez- Quintela, J Rivas, Y Tokura and S B Osnofj Phys Rev. S8B 3233 (1998)[8] MSSeehra,MMIbrahim,VSureshBabuandSSnnivasanJ Ph,\, ; Cond. Matter % 11283 (1996)[9 j A1 Shames, E Rozenberg, G Gorodetsky, J Pclleg and B K Chaudhun Solid State Commun, 107 91 (1998)[10] W H McCarroll, Ian D Fawcett, M Greenblatt and K V Ramanujachary J  Solid State Cliem. 146 88 (1999)[111 A 1 Shames, E Hozenbeig, G Gorodetsky, B Revzin, D Mogilyaiiski J Pelleg and I Felner JMMM 203 259 (1999)[12] C A Ramos, M T Causa, M Tovar, X Obrados and S Pinol Ihui 177-181 867 (1998)[13] SB Oseroff, M Tonkachvili, J Singley, S Ali, S-W Cheong iuid S Schultz Phys. Rev B53 6521 (1996)[14] G Papavassiliou, M Fardis, F Miha, A Simopoloulos, G Kallias, M Pissas, D Niarchos, N loannidis, C Dimitropoulos and J Dulir.sd Phys Rev B55 15000 (1997)[ 15 j Cz Capusta, P C Riedi, W Kochemba, C J Tomka, M R Ibiuia I M Dc Teresa, M Virct and J M D Coey J Ph\s Cond Maun 11 4097 (1999)[16] J -P Renard and A Anane Mater Suence Engg B63 22

Electron Magnetic Resonance in Doped Colossal Magnetoresistive Manganites

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Electron Magnetic Resonance in Doped Colossal Magnetoresistive Manganites

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