Crystal and magnetic structure of theLa1−xCaxMnO

Abstract

Crystal and magnetic structure of the La 1−x Ca x MnO 3 compound (x = 0.8, 0.85). We studied the crystal and magnetic structure of the La1−xCaxMnO3 compound for x = 0.8 and x = 0.85. At T = 300 K both samples are paramagnetic with crystallographic symmetry P nma. At low temperatures they undergo a monoclinic distortion from orthorhombic P nma-type structure with ap √ 2 × 2ap × ap √ 2 to a monoclinic structure with (ap √ 2 × 2ap × ap √ 2, β = 90 + ε ∼ 91.4 o ) and P 21/m space group below TN . The onset of the structural transformation coincides with the development of the C-type long range antiferromagnetic order with propagation vector k = ( 1 2 , 0, 1 2 ). The monoclinic unit cell allowed us to determine the direction of the Mn magnetic moment with respect to the crystallographic axes: it is perpendicular to the propagation vector, m ⊥ k = ( 1 2 , 0, 1 2 ). The amplitude of the ordered magnetic moment at T = 1.6 K is found to be 2.53(2) and 2.47(2)µB for x = 0.8 and 0.85, respectively.

Inhomogeneous magnetism in La-dopedCaMnO3. II. Nanometric-scale spin clusters and long-range spin canting

“…Nevertheless, the pure FM metallic state is never stabilized for La-doped CaMnO 3 , due to the gradual emergence of the orbitally-ordered C-AFM state for x 0.06, which competes with the G-AFM + FM state through a first-order phase transition, as explored in the following paper 26 . This competition leads to mesoscopic magnetic and crystallographic phase separation over a large x-and T -interval, and finally to the stabilization of the C-AFM phase for 0.16 x 0.20 26,32,33,34 .…”

Magnetic study of CaMn0.96Mo0.04O3, canting vs. phase separation

“…Particular attention was paid to the unexpected behaviour observed for the low electron-doped regime, where a ferromagnetic (FM) component develops together with G-type antiferromagnetism (AFM), for which each Mn is AFM coupled with the six Mn nearestneighbours. This ability of G-type AFM to allow a FM component is discussed in terms of canting or phase separation [5], the latter being more often admitted [6][7][8][9][10][11][12][13]. This particular state, resulting from competing interactions, leads to unusual signatures in the magnetic characterizations [14] that are also observed in manganites with similar Mn valence, but which are obtained by substitution on the Mn site instead of the Ln one.…”

Pressure effects on magnetic and transport properties of electron-dopedLa1−xCaxMnO3<

“…Nevertheless, recently, ND data have revealed static JT distortion in La 1−x Ca x MnO 3 ͑x = 0.8, 0.85͒ with low content of Mn 3+ . 10 For the study of the pressure effect on magnetic and transport properties of electron-doped manganites, we have chosen two compounds La 1−x Ca x MnO 3 ͑x = 0.8, 0.9͒ that show distinct magnetic and transport properties at ambient pressure and have been ex-tensively studied recently by ND measurements. [10][11][12][13] Measurements performed under pressure allowed us to find which interactions play a dominant role in a given system, i.e., we were able to distinguish if the dominant is competing AFM-FM or orbital ordering.…”

“…It appears that the magnetization sharply rises on cooling at about 107 K, a critical temperature that coincides with the Néel temperature. [10][11][12][13] Note that M͑T͒ displays a minimum around T Ϸ 85 K, at ambient pressure in magnetic field of 15 kOe, which disappears at P = 10.2 kbar ͓inset to Fig. 1͑a͔͒.…”