Interaction between thed-Shells in the Transition Metals. II. Ferromagnetic Compounds of Manganese with Perovskite Structure

Low temperature synthesis, and magnetic and magnetotransport properties of a (La1 xLux)0.67Ca0.33MnO3(0 x 0.12) system

“…In spite of similar sizes of Y +3 and Lu +3 , a difference in structural and thermal properties of the hexagonal YMnO 3 and LuMnO 3 is observed 16 . The out-of-plane lattice constant, c, continuously decreases with temperature in the range 300K to 1000K for YMnO 3 , while it remains constant with temperature in that range for LuMnO 3 . An entirely different variation of excess specific heat, ∆C p /T , a quantity related to the magnetic contribution of the system and obtained by the subtraction of the lattice specific heat from the net specific heat of the system, with temperature is observed 17 in the two 3 compounds, YMnO 3 and LuMnO 3 .…”

“…have been the subject of intense research since the discovery of colossal magnetoresistance (CMR) in this class of compounds 1,2 . The parent compound, LaMnO 3 , is an antiferromagnetic insulator in which Mn is present in a single oxidation state (Mn +3 ). But substitutions by a divalent alkaline earth metal ion like Ca, Sr, Ba or Pb at the trivalent rare earth site causes mixed valency of Mn ions and transforms this compound to a ferromagnetic metal.…”

“…But substitutions by a divalent alkaline earth metal ion like Ca, Sr, Ba or Pb at the trivalent rare earth site causes mixed valency of Mn ions and transforms this compound to a ferromagnetic metal. The doped charge carriers (holes) mediate the ferromagnetic interactions between the localized spins (t 2g ) associated with the variable valency Mn ions (Mn +3 /Mn +4 ) in the crystallographically equivalent sites through the double exchange (DE) mechanism 3 . Since the ferromagnetic Curie temperature (T C ) and the metal insulator transition temperature (T MI ) in such compounds are related to the strength of the transfer integral between Mn +3/+4 through the Mn +3 -O -Mn +4 path, there is a strong interplay between the structural, magnetic and transport properties.…”

Crystal Structure and Chemical Characterization of La0.7Sr0.3Mn0.7Ti0.3-xAlxO3 (0 ≤ x ≤ 0.15) Compounds

“…The interplay between ferromagnetism and electroconductivity in these compounds has been explained using the double exchange model [2]. This model suggests real electron transfer from Mn 3+ (Co 3+ ) to Mn 4+ (Co 4+ ) while this mechanism is effective only for the mixedvalence systems.…”

Mean-field theory of charge ordering and phase transitions in the colossal-magnetoresistive manganites

“…Work in the 1950s and 1960s elucidated the nature of the magnetic ordering in these systems [1][2][3] and uncovered the role of the double-exchange mechanism in stabilizing ferromagnetic phases [4][5][6]. Recent work, motivated by the observation [7][8][9][10][11][12] of colossal magnetoresistance (CMR) in this class of compounds, has focused on their intriguing magnetic and conduction properties.…”