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Electric-field control of strain-mediated magnetoelectric random access memory
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10.1063/1.3373593
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Affiliations:
1 Department of Materials Science and Engineering, State Key Lab of New Ceramics and Fine Processing, Tsinghua University, Beijing 100084, China
a) Author to whom correspondence should be addressed. Electronic mail: cwnan@tsinghua.edu.cn.
J. Appl. Phys. 107, 093912 (2010)
/content/aip/journal/jap/107/9/10.1063/1.3373593
http://aip.metastore.ingenta.com/content/aip/journal/jap/107/9/10.1063/1.3373593

## Figures

FIG. 1.

(a) Schematic diagram of a SME-RAM element. and show the initial magnetization orientations in the upper hard layer and the bottom free layer of a MTJ unit, respectively. A transverse electric field is applied to the FE layer with a spontaneous polarization to generate a 90° in-plane magnetization switching. (b) the 90° in-plane magnetization switching process in the free layer with its length , width , and thickness directions along the three principle crystal axes, i.e., the [010], [100], and [001], respectively.

FIG. 2.

Free energy density change in the (001)-oriented free layer as a function of (a) the direction cosine and (b) the direction cosine under different electric fields for a forward and back magnetization switching process, respectively. The solid dots indicate the two energy minima at and . (c) Direction cosine of the magnetization vector in the (001)-oriented free layer as a function of a transverse electric field . The arrows with ellipses in (a)–(c) denote the magnetization orientations. (d) a hysteresis loop of the device resistance dependent on the applied electric field accompanied with the magnetization switching, with the inset showing the profile of the device structure. The white symbol denotes a 90° in-plane magnetization.

FIG. 3.

Free energy density change in the (001)-oriented CFO free layer as a function of (a) the direction cosine and (b) the direction cosine under different electric fields for a forward and back magnetization switching process, respectively. The solid dots indicate the two energy minima at and . (c) Direction cosine of the magnetization vector in the (001)-oriented CFO free layers as a function of a transverse electric field . The arrows with ellipses in (a)–(c) denote the magnetization orientations. (d) a hysteresis loop of the device resistance dependent on the applied electric field accompanied with the magnetization switching, with the inset showing the profile of the device structure. The white symbol denotes a 90° in-plane magnetization.

FIG. 4.

Free energy density change in the (001)-oriented Ni free layer as a function of (a) the direction cosine , and (b) the direction cosine , under different electric fields for a forward and back magnetization switching process, respectively. The solid dots indicate the two energy minima at and (0.799). (c) Direction cosine of the magnetization vector in the (001)-oriented Ni free layers as a function of a transverse electric field . The arrows with ellipses in (a)–(c) denote the magnetization orientations. (d) A gradual electric-field-induced resistance change accompanied with the magnetization switching, with the inset showing the profile of the device structure. The white symbol denotes a 90° in-plane magnetization.

FIG. 5.

Free energy density change in the (001)-oriented free layer as a function of (a) the direction cosine and (b) the direction cosine under different electric fields for a forward and back magnetization switching process, respectively. The solid dots indicate the two energy minima at and (0.754). (c) Direction cosine of the magnetization vector in the (001)-oriented free layers as a function of a transverse electric field . The arrows with ellipses in (a)–(c) denote the magnetization orientations. (d) A gradual electric-field-induced resistance change accompanied with the magnetization switching, with the inset showing the profile of the device structure. The white symbol denotes a 90° in-plane magnetization.

FIG. 6.

Direction cosine of the magnetization in polycrystalline free layers: (a) , (b) CFO, (c) Ni, and (d) , as a function of a transverse electric field . The arrows within ellipses denote the magnetization orientations.

FIG. 7.

Gradual electric-field-induced resistance changes in SME-RAM devices with polycrystalline free layers: (a) , (b) CFO, (c) Ni, and (d) . The inset shows the profile of the device structure. The white symbol denotes a 90° in-plane magnetization.

FIG. 8.

(a) Direction cosine of the magnetization in the (001)-oriented free layer with different aspect ratios and (b) corresponding junction resistance, as a function of a transverse electric field . Dependence of and on (c) the thickness and (d) the width of the (001)-oriented free layer.

## Tables

Table I.

Materials parameters (Refs. ), i.e., magnetocystalline coefficient , magnetoelastic coupling coefficient and , for iron-cobalt alloy , CFO, nickel (Ni), and magnetite , used for the present numerical calculations.

Table II.

The critical electric fields for a forward and back switching process, i.e., and , and the corresponding barriers heights, i.e., and , for the cases with (001)-oriented free layers.

Table III.

The critical switching electric fields and the saturated electric fields, i.e., and , for the cases with polycrystalline free layers.

Table IV.

The critical forward and back switching electric fields, i.e., and , for the SME-RAMs with PZN–PT, , and as the FE layers at . The (001)-oriented and CFO films are used for the magnetically free layers.

/content/aip/journal/jap/107/9/10.1063/1.3373593
2010-05-06
2014-04-24

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