Abstract
Large magnetoresistive materials are of immense interest for a number of spintronic applications, such as the development of high-density magnetic memory devices, magnetic sensors, and magnetic switches. Colossal magnetoresistance, in which the resistivity changes by several orders of magnitude (~ 104%) in an external magnetic field, occurs mainly in phase-separated oxide materials, namely, manganites, owing to the phase competition between the ferromagnetic metallic and antiferromagnetic insulating regions. Can the magnetoresistance be further enhanced by tuning the volume fraction of the two phases? In this work, we report a huge colossal magnetoresistance along with an ultrasharp metamagnetic transition in a half-doped Sm0.5Ca0.25Sr0.25MnO3 manganite compound by suitably tuning the volume fraction of the competing phases. The obtained magnetoresistance value at 10 K is as large as ~ 1013% in a 30 kOe external magnetic field and ~ 1015% in a 90 kOe external magnetic field and is several orders of magnitude higher than any other observed magnetoresistance value reported thus far. Using model Hamiltonian calculations, we have shown that the inhomogeneous disorder, deduced from tunneling electron microscopy, suppresses the CE-type phase and seeds the ferromagnetic metal in an external magnetic field.
Highlights
For the last several years, the search for materials with large magnetoresistances (MRs) and studies on related phenomena have been in the forefront of worldwide research activity[1,2,3,4,5,6,7] owing to their widespread application in the field of magnetic sensors, magnetic memory devices, magnetic switches, etc[8,9,10,11,12]
An insulating state is observed in the charge-ordered antiferromagnetic (CO-AFM) sample, which generally appears near half doping
The CO-AFM state can be weakened by introducing ferromagnetic proximity as follows: (i) by effectively increasing the bandwidth of the eg electrons via substitution of larger cations at the A-sites[13,14,15,16], (ii) via B-site doping (e.g., Cr or Ru doping on Mn sites)[17,18,19], and (iii) by making FM-AFM core-shell nanostructures[20,21,22]
Summary
For the last several years, the search for materials with large magnetoresistances (MRs) and studies on related phenomena have been in the forefront of worldwide research activity[1,2,3,4,5,6,7] owing to their widespread application in the field of magnetic sensors, magnetic memory devices, magnetic switches, etc[8,9,10,11,12]. An insulating state is observed in the charge-ordered antiferromagnetic (CO-AFM) sample, which generally appears near half doping. The critical magnetic field, which is required to destabilize the CO-AFM state, increases with decreasing bandwidth. The CO-AFM state can be weakened by introducing ferromagnetic proximity as follows: (i) by effectively increasing the bandwidth of the eg electrons via substitution of larger cations at the A-sites[13,14,15,16], (ii) via B-site doping (e.g., Cr or Ru doping on Mn sites)[17,18,19], and (iii) by making FM-AFM core-shell nanostructures (or nanoparticles)[20,21,22]. Inducing a ferromagnetic phase fraction in an antiferromagnetic manganite or, in other words, engineering electronic phase separation is an effective tool to enhance the MR. A great amount of effort has been devoted to control the electronic phase separation in bulk and low dimensional manganites[23,24,25,26,27,28,29]
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