Magnetic and Crystallographic Transitions in ${Sc}^{3 +}$ , ${Cr}^{3 +}$ , and ${Ga}^{3 +}$ Substituted ${Mn}_{2}$ $O_{3}$

X-ray diffraction and magnetic susceptibility measurements have been used to determine the phase diagrams, including magnetic phases, of the systems

{({Mn}_{1 - x} M_{x})}_{2} O_{3}

, where

M \equiv {Sc}^{3 +}, {Cr}^{3 +}, {Ga}^{3 +}

. Maximum values of

x

are 0.02, 0.13, and 0.27, respectively. Of the substituent ions

{Cr}^{3 +}

{Fe}^{3 +}

{Sc}^{3 +}

and

{Ga}^{3 +}

{Cr}^{3 +}

reduces the crystallographic transition temperature least rapidly,

{Ga}^{3 +}

and

{Sc}^{3 +}

, most rapidly.

{Ga}^{3 +}

ion substitution reduces the upper Néel temperature

T_{N 1}

about as rapidly as does

{Fe}^{3 +}

ion substitution to

x \approx 0.06

, and it appears that if specimens could be made to

x > 0.38

, there would be no more magnetic ordering in the

{({Mn}_{1 - x} {Ga}_{x})}_{2} O_{3}

system.

{Cr}^{3 +}

ion does not decrease

T_{N 1}

as drastically as either

{Ga}^{3 +}

{Fe}^{3 +}

; at 12-at%

{Cr}^{3 +}

T_{N 1}

is 68 K, while for an equal amount of

{Ga}^{3 +}

, for example, it is 40 K; for 12-at.%

{Fe}^{3 +}

, it is 25 K. These results imply that in this structure, empty

t_{e_{g}}

orbitals are particularly important to the magnetic interactions, and that

This publication has 14 references indexed in Scilit:

Magnetic and Crystallographic Transitions in Sc3+, Cr3+, and Ga3+ Substituted Mn2O3