Exchange Bias Effect and Suppression of Charge Ordering Induced by a Surface Phase Separation in La_0.25Ca_0.75MnO₃ Nanowires

Abstract

The microstructure and magnetic properties of the polycrystalline La 0.25 Ca 0.75 MnO 3 nanowires with diameter of about 60 nm prepared by a sol-gel template method were studied with use of X-ray diffraction, transmission electron microscopy, and superconducting quantum interference device magnetometry. Compared with the robust charge ordering (CO) state with CO transition temperature T CO ≈ 240 K in the bulk counterpart, the CO is suppressed with T CO ≈ 138 K and CO transition becomes wide, at the same time the ferromagnetic (FM) cluster glass state and the exchange bias effect are detected in La 0.25 Ca 0.75 MnO 3 nanowires. This exotic behavior is attributed to the uncompensated surface spins which change the spin configuration of nanowires and enhance the e g charge density at the surface compared to bulk compound and thereby induce the FM cluster glass state as well as exchange bias effect, and weaken the CO.

High magnetic field phase diagram in electron-doped manganites La0.4Ca0.6Mn1−yCryO3

“…In Sm 1−x Ca x MnO 3 (0.5 < x ≤ 0.85)12, the CO melting magnetic field was revealed to decrease monotonously with increasing x , while the e g electron density decreases simultaneously. Recently, although the CO state is very robust in La 1−x Ca x MnO 3 (0.5 < x ≤ 0.87)1314, exceptional CO breaking and ferromagnetism upon size reduction (down to nano-scale) or impurity doping was broadly reported151617181920. Moreover, photo-induced CO melting was observed in La 0.42 Ca 0.58 MnO 3 , and the threshold fluence for melting the CO phase was revealed to be significantly lower than that for hole-doped La 1/4 Pr 3/8 Ca 3/8 MnO 3 2122, which seems inconsistent with the fact that an electron-doped material has a much more stable CO state1323.…”

Evidence of exchange bias effect originating from the interaction between antiferromagnetic core and spin glass shell

“…7 Although some studies suggested the interface coupling interaction between core and shell in one-dimensional (1D) AFM nanostructures can induce EB effect, the evidence to support this coupling effect has not been presented till now. [8][9][10][11][12] So, to find the proof of this coupling effect is an important work. In this paper, SG behavior and EB effect of single crystallization SrMn 3 O 6Àx nanoribbons synthesized via a self-sacrificing template process is studied in details.…”

Synthesis and magnetic properties of antiferromagnetic Li2MnO3 nanoribbons

“…Furthermore, the EB effect has also been found in 1D magnetic nanostructures, such as Co 3 [18]. In most cases, the EB in the nanostructures of AFM materials can be attributed to the presence of uncompensated surface spins and a core-shell phenomenological model is used to describe the magnetic structure of AFM nanomaterials [1,6,18,[27][28][29][30][31]. Considering the surface ferromagnetism in Fig.…”