Continuously tunable magnetic phase transitions in the DyMn1−xFexO3 system

Abstract

The structure and magnetic properties of perovskite DyMn1−xFexO3 samples have been studied. Static orbital orderings are expected to exist in samples with x ≤ 0.2 due to strong Jahn-Teller distortion, which become less stable as x increases and probably disappears in samples with x > 0.5. The antiferromagnetic transition temperature increases as x increases. At the composition x > 0.5, spin reorientation starts to appear. Meanwhile, the spin reorientation temperature and the antiferromagnetic Néel temperature gradually separate and widen the temperature range of the magnetic metastable state between these two transitions. The magnetic competition is discussed based on exchange interaction and Dzyaloshinsky-Moriya interaction.

Dielectric relaxation in the DyMn1−xFexO3 system

“…With increasing Fe content, the b-axis parameter of the unit cell becomes monotonically shorter, the c-axis parameter becomes longer in a linear way, and the a-axis parameter only increases slightly. Consistent with our previous work, 18 antiferroic JT orbital ordering) superimposed on high temperature O-type (i.e., not JT distorted) orthorhombic structure. 19,20 As x > 0.33, a > c/ ffiffi ffi 2 p is found.…”

“…18 The first transition between x ¼ 0.2 and x ¼ 0.33 is consistent with the structural change where static orbital ordering disappears and is replaced by weaker dynamic orbital ordering due to weaker Jahn-Teller distortion. The transition between x ¼ 0.5 and x ¼ 0.6 is found to correspond to the disappearance of dynamic orbital ordering and the appearance of spin reorientation.…”

“…Otherwise, the magnetic orderings seem to affect the relaxation as well. With x increasing from 0, the E a increases until x ¼ 0.6, during which the AFM transition temperature increases from 39 K to 400 K. 18 The enhanced superexchange interaction restricts the electron transfer and consequently introduces higher E a . For x !…”

“…0.6, spin reorientation (SR, from the canted AFM state to the collinear AFM state in this system) appears, and the transition temperature of SR decreases with increasing x. 18 The relaxation process becomes easier because the canted AFM states allow a higher chance for electron transfer, compared with the collinear AFM state, and this effect introduces a smaller E a . The small amounts of Mn 4 þ /Mn 2þ and Fe 2þ , due to the inevitable presence of oxygen defects, which occur often in manganites 22 and ferrites, 23 are likely to be responsible for the relaxation process.…”

“…In the multiferroic DyMn 1-x Fe x O 3 system, there is continuous structural and magnetic evolution. 18 The static JahnTeller orbital ordering becomes unstable and is replaced by dynamic orbital ordering as x increases from 0 to 0.5, while the collinear AFM transition temperature shifts to higher temperature. Orbital ordering disappears in the samples with x > 0.5, and the samples show canted AFM ordering and experience spin reorientation from canted AFM to collinear AFM at relatively low temperature.…”