Abstract

In terms of the two-phase nanoparticles model, the effect of mechanical stress on the magnetic state of both uniaxial and multiaxial heterophase magnetic is investigated. The spectrum of critical fields of reversal of phases' magnetic moments was calculated and phase diagrams were drawn to assess the effect of mechanical stress on the degree of metastability of two-phase nanoparticles' magnetic states. By the example of epitaxial cobalt-coated <svg style="vertical-align:-3.56265pt;width:8.6374998px;" id="M1" height="12.175" version="1.1" viewBox="0 0 8.6374998 12.175" width="8.6374998" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,7.675)"><path id="x1D6FE" d="M478 372q0 -39 -31 -97t-61 -98t-78 -98q-45 -55 -73 -102q-13 -79 -13 -197q-11 -11 -43.5 -25.5t-53.5 -15.5l-15 17q5 35 26 101.5t47 123.5q8 72 -1.5 174.5t-37.5 178.5q-14 37 -29 37q-20 0 -67 -65l-25 21q37 60 73 90.5t63 30.5q47 0 72 -112q13 -56 17.5 -141.5&#xA;t0.5 -143.5h2q155 193 155 297q0 26 -12 47q-5 8 -5 15q0 16 12.5 27t29.5 11q21 0 34 -21t13 -55z" /></g> </svg>-Fe<sub >2</sub>O<sub >3</sub> particles, a theoretical analysis of the effect of uniaxial mechanical stress on the magnetization of a system of noninteracting heterophase nanoparticles is investigated. It was shown that tension reduced and compression increased coercive force <svg style="vertical-align:-3.3907pt;width:20.487499px;" id="M2" height="15.4" version="1.1" viewBox="0 0 20.487499 15.4" width="20.487499" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x1D43B" d="M865 650q-1 -4 -4 -14t-4 -14q-62 -5 -77 -19.5t-29 -82.5l-74 -394q-12 -61 -0.5 -77t75.5 -21l-6 -28h-273l8 28q64 5 82 21t29 76l36 198h-380l-37 -197q-11 -64 0.5 -78.5t79.5 -19.5l-6 -28h-268l6 28q60 6 75.5 21.5t26.5 76.5l75 394q13 66 2 81.5t-77 20.5l8 28&#xA;h263l-6 -28q-58 -5 -75.5 -21t-30.5 -81l-26 -153h377l29 153q12 67 2 81t-74 21l5 28h268z" /></g> <g transform="matrix(.012,-0,0,-.012,14.975,15.187)"><path id="x1D450" d="M383 397q0 -32 -35 -49q-12 -6 -23 8q-37 45 -84 45t-90 -71q-40 -65 -40 -167q0 -57 22 -86t59 -29q38 0 81.5 24.5t69.5 51.5l16 -21q-44 -53 -104 -84t-109 -31q-56 0 -89.5 41t-33.5 117q0 61 30 124t79 105q33 28 81 50.5t86 22.5q34 0 59 -15.5t25 -35.5z" /></g> </svg>, while the residual saturation magnetization <svg style="vertical-align:-3.39069pt;width:16.9625px;" id="M3" height="15.4" version="1.1" viewBox="0 0 16.9625 15.4" width="16.9625" xmlns:xlink="http://www.w3.org/1999/xlink" xmlns="http://www.w3.org/2000/svg"> <g transform="matrix(.017,-0,0,-.017,.062,11.112)"><path id="x1D43C" d="M414 650l-6 -28q-63 -4 -78.5 -17.5t-27.5 -71.5l-77 -416q-11 -58 0.5 -71.5t77.5 -17.5l-5 -28h-275l8 28q63 4 79.5 18.5t27.5 70.5l80 416q11 57 -2 71t-81 18l6 28h273z" /></g> <g transform="matrix(.012,-0,0,-.012,7.487,15.187)"><path id="x72" d="M181 342h2q63 107 121 107q24 0 41 -16t17 -34q0 -34 -32 -49q-17 -7 -26 2q-21 20 -43 20q-20 0 -42 -22t-38 -63v-183q0 -50 12.5 -62t69.5 -16v-26h-230v26q47 5 58 17t11 61v207q0 49 -9 60.5t-53 16.5v23q74 12 141 40v-109z" /></g><g transform="matrix(.012,-0,0,-.012,11.902,15.187)"><path id="x73" d="M319 325l-25 -7q-33 99 -103 99q-29 0 -47 -19.5t-18 -49.5t22 -49.5t62 -36.5q63 -26 95 -57t32 -79q0 -64 -50 -101t-115 -37q-35 0 -67.5 10.5t-46.5 23.5q-5 11 -11 51t-6 67l27 5q14 -53 46.5 -88.5t75.5 -35.5q29 0 50 19.5t21 50.5t-19.5 51.5t-59.5 39.5&#xA;q-28 12 -46 22.5t-38.5 27t-30.5 38.5t-10 49q0 54 42.5 92t109.5 38q48 0 88 -18q6 -15 13 -50.5t9 -55.5z" /></g> </svg> was not changed under the influence of mechanical stress.

Highlights

  • One of the factors that influence the magnetization is the heterophase of nanoparticles determining magnetic properties of nanodispersed materials

  • Polymer and nonmetallic core/shell nanoparticles are a new class of materials for electronics, for example, the organic lightemitting diodes (OLEDs), organic photovoltaics (OPVs), sensors, and organic field effect transistors (OFETs) [33,34,35]

  • Carriers of magnetic memory elements’ magnetic properties may be represented by iron particles [36,37,38] exposed to surface oxidation or magnetic nanoparticles coated with other material, such as cobalt-coated γ-Fe2O3 particles [39,40,41]

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Summary

Introduction

One of the factors that influence the magnetization is the heterophase of nanoparticles determining magnetic properties of nanodispersed materials. Carriers of magnetic memory elements’ magnetic properties may be represented by iron particles [36,37,38] exposed to surface oxidation or magnetic nanoparticles coated with other material, such as cobalt-coated γ-Fe2O3 particles [39,40,41]. Along with the exchange interaction, there is mechanical stress at the interphase interface that is able to alter magnetic states of both phases due to size differences of neighboring phases’ lattices. We attempt to expand the model [58, 59] to multiaxis dual-phase particles and studies of the effect of mechanical stress on the magnetic states and magnetic properties of systems of such particles

The Model of a Uniaxial Two-Phase Nanoparticle
Static States of the Magnetic Moment of Uniaxial Nanoparticle
Magnetic States of Multiaxis Two-Phase Nanoparticle
Diagrams of the Magnetic States of Heterophase Nanoparticles
Magnetization of the System of Two-Phase Nanoparticles
The Effect of Mechanical Stress on the Magnetization Curve and Hysteresis
Findings
Conclusions
Full Text
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