Конспект лекций по статистической физике. Коренблит С.Э - 151 стр.

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‚§ ¨¬®¤¥©á⢨¥ ¬¥¦¤ã ᮡ®© ᯨ­®¢ëå ¬ £­¨â­ëå ¬®¬¥­â®¢ ï¥âáï
㦥 ­¥«¨­¥©­ë¬ íä䥪⮬: ª ¦¤ë© ᯨ­ ­ 室¨âáï, ­ á ¬®¬ ¤¥«¥, ¢
¬ˆªà®áª®¯¨ç¥áª®¬ ¯®«¥ Heff = H + H, ᮧ¤ ­­®¬, ¢ ⮬ ç¨á«¥, ¢á¥¬¨
®áâ «ì­ë¬¨ ᯨ­ ¬¨. ‘®£« á­® ‚¥©ááã, ¨¬¥îé ïáï ­ ¬ £­¨ç¥­­®áâì ¨
ᮧ¤ ¥â íä䥪⨢­® â ª®¥ ¤®¯®«­¨â¥«ì­®¥, ¯à®¯®à樮­ «ì­®¥ ¥© ¬ £­¨â-
­®¥ ¯®«¥: H =) M. ’®£¤ ¯®«­®¥ íä䥪⨢­®¥ ¯®«¥ Heff ­ ¯®¬¨­ ¥â
¬€ªà®áª®¯¨ç¥áª®¥ ¢ëà ¦¥­¨¥ ¤«ï ¬ £­¨â­®© ¨­¤ãªæ¨¨ B = H + 4M,
­® ®­® ï¥âáï á ¬®á®£« ᮢ ­­ë¬, ¢ ⮬ á¬ëá«¥, çâ® á ¬ ­ ¬ £­¨ç¥­-
­®áâì ®¯à¥¤¥«ï¥âáï ¨§ ãà ¢­¥­¨ï (14.53) 㦥 á í⨬ á।­¨¬ ¯®«¥¬ ‚¥©-
áá Heff ¢ à£ã¬¥­â¥ ä㭪樨 ‹ ­¦¥¢¥­ LS (y), (LS (0) = 0, LS (1) = 1):
                                   !              M        !
                                                   0 Heff
   M(T; H) = nB th kT (H + M) S=1=2
                         B
                                      (= M0 LS n kT : (14.55)
à¨ H = 0 íâ® ¤ ¥â âà ­á業¤¥­â­®¥ ãà ¢­¥­¨¥ ¤«ï ᯮ­â ­­®© ­ ¬ £-
­¨ç¥­­®á⨠M, ®â¢¥ç î饩 ä¥à஬ £­¨â­®¬ã á®áâ®ï­¨î [5]x78:
 M = L M0 M ! ; ¨«¨: T y = L (y) =) th y  y y3 ; £¤¥: (14.56)
 M 0 S n kT                        S   S=1=2          3
       M =) B M ;  = M0 =) nB ; M0 = g S =)  : (14.57)
 y = TM
                               2        2
           S=1=2 kT                                 B S=1=2 B
         0                  n k S=1=2 k       n
Žç¥¢¨¤­®, ¯à¨ T < TC  L0S (0), ªà®¬¥ y  0, ¢®§­¨ª­¥â à¥è¥­¨¥ á yC 6= 0
(¨á. 14.1). € â.ª. yC  1 ¤«ï T ' TC , â® ¨§ (14.56) ¨ LS ( y) = LS (y):
                                          v
                                          u                !
                                            L
 LS (y)  LS (0)y by   y; yC (T )   b 1 T  LM
                         T                u  0 (0)      T           (T ) :
            0         3                   t  S
                                                         C      0 (0)M0
                                                                S
                                                                     (14.58)
„¨ää¥à¥­æ¨àãï ãà ¢­¥­¨¥ (14.55) ¯® H ¨ ¯®« £ ï H = 0; á ãç¥â®¬ yC (T )
¨§ (14.56), ­ ©¤¥¬ ¯®¢¥¤¥­¨¥ ¢®á¯à¨¨¬ç¨¢®á⨠¤«ï «î¡ëå T (áà. (14.54)):
     T = nMkT0 L0S (y)(1 + T ); T = (TLS (Ly0)(y))
                2                               0
                                                                   : (14.59)
                                                   S    y=y C (T )
à¨ T  TC ¨¬¥¥¬ «¨èì à¥è¥­¨¥ (14.56) yC (T )  0, â.¥. (á¬. ¨á. 14.2):
  L0S (y) T TC =) L0S (0); çâ® ¤ ¥â § ª®­: T T>TC = (TTC T ) ; (14.60)
                                               H=0
                                                                 C
{ Šîà¨-‚¥©áá (áà. (14.54)) á ⥬¯¥à âãன ŠîਠTC ä §®¢®£® ¯¥à¥å®¤
2-£® த ¨§ ¯ à ¬ £­¨â­®£® á®áâ®ï­¨ï ¯à¨ T > TC ¢ ä¥à஬ £­¨â­®¥,
¯à¨ T < TC , £¤¥ ¢®á¯à¨¨¬ç¨¢®áâì (14.59) â¥à¯¨â à §àë¢ 2-£® த (14.60).