Significant enhancement of magnetoresistance with the reduction of particle size in nanometer scale

Abstract

The Physics of materials with large magnetoresistance (MR), defined as the percentage change of electrical resistance with the application of external magnetic field, has been an active field of research for quite some times. In addition to the fundamental interest, large MR has widespread application that includes the field of magnetic field sensor technology. New materials with large MR is interesting. However it is more appealing to vast scientific community if a method describe to achieve many fold enhancement of MR of already known materials. Our study on several manganite samples In present days science based society largely depends on several gadgets where magnetic field sensors play crucial role. The primary requirement for magnetoresistive sensor is the large magnetoresistance. Last two decades perovskite manganites was in the fore-front of the experimental research and resulted several thousand research articles with the primary focus on large magnetoresistance (MR). However, in manganites most of the cases large magnetoresistance occurs at very high (several tesla or more) magnetic field. The requirement of the large external magnetic field severely restrict the use of manganites as magnetic field sensor. Our findings in this manuscript show how the MR of the same material can be increased drastically even at the lower magnetic field.The doped perovskite manganite is generally represented by the formula R 1−x B x MnO 3 , where 'R' is a trivalent rare earth and 'B' is a bivalent element. Numerous fascinating properties of the doped manganites were observed depending on the bivalent element B and its doping concentration x. In addition to the metal-insulator transition and colossal magnetoresistance, doped manganite compounds usually show a generic phenomenon of charge ordering close to the doping concentrations x ~ 1 2 , 3 8 and some other concentrations. The charge-ordering (CO) is the real space ordering of the Mn 3+ and Mn 4+ ions and it is generally followed by an antiferromagnetic transition with the lowering of temperature. The high resistive insulating behavior with lowering the temperature below the charge-ordering transition temperature is also a generic behavior of the charge-ordered manganites. In the presence of external perturbations like magnetic field, electric field, x-ray irradiation etc., the high resistive insulating state transforms into a low resistive metallic state as a results of destabilization of the charge ordering. The magnetic field-induced destabilization of the charge ordering leads to the gigantic change of the resistance which is known as colossal magnetoresistance. The required magnetic field to destabilize the charge ordered state depends upon the electronic band width of the compounds and the charge-ordered state is more robust for lower band width system. During the last two decades, magnetoresistive properties of several doped perovskite manganites were extensively studied 1-8 . To consider manganites for technological purposes such as magnetic field sensor, the hi...

Magnetic frustration induced large magnetocaloric effect in the absence of long range magnetic order

“…The first term in the equation corresponds to ferromagnetic volume fraction and origin of the linear term is the combining effect of antiferromagnetic and paramagnetic volume fraction. Such type of analysis have also been performed for earlier reported systems with ferromagnetic and antiferromagnetic interactions 38 . As seen from inset II of Fig.…”

Magnetic and electric properties of wrinkled manganite films derived by sol‐gel method

“…As grain size decreases, the intergrain conduction plays more dominant role in the resistivity, therefore flat films with smaller grains have higher resistivity. Moreover, it is accepted that magnetoresistance (MR) can be enhanced by magnetic induced reduction of scattering effect at grain boundaries with smaller grains . However, as shown in Figure B, the magnetoresistance (MR) of wrinkled films and flat films are almost at the same value, and the wrinkled films even have a little bit higher MR values, which may be ascribed to the compressive stress.…”

“…Perovskite manganite La 0.7 Sr 0.3 MnO 3 (LSMO) film has attracted great interest in potential application in magnetic field sensors, magnetic random access memories, and magnetoelectric and spintronic devices, for the abundant physical properties resulted from the interactions between the charge, spin, orbital degrees of freedom, and lattice vibrations of this material . It has been widely accepted that compressive stress on bulk perovskite manganite materials can increase magnetization, Curie temperature ( T c ), peak resistivity temperature ( T p ), and decrease resistivity by reducing Jahn‐Teller distortion, namely decreasing Mn‐O bond length and increasing Mn‐O‐Mn bond angle .…”

Anomalous Magnetotransport Properties of Bi Doped La0.67Sr0.33MnO3

“…While doping Bi in ferromagnetic metallic manganites, the charge ordering is induced and gives the phase separation. The charge ordering destabilizes in the applied magnetic field . Hence in Bi3 , the second low‐temperature upturn induced by the applied magnetic field ( T LH ) could be due to the charge ordering effect.…”