# Electromagnetic Radiation Effects on MgO-Based Magnetic Tunnel Junctions: A Review

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## Abstract

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## 1. Introduction

#### 1.1. Tunnel Magnetoresistance

#### 1.2. Applications of MTJs

#### 1.2.1. Electronics

#### 1.2.2. Energy Harvesting

#### 1.2.3. Energy Storage

#### 1.3. Irradiation

#### 1.3.1. Natural Radiation Sources

#### 1.3.2. Artificial Radiation Sources

#### 1.3.3. Radiation Units

#### 1.4. Properties of MTJ Materials

#### 1.4.1. Magnesium Oxide Barrier

#### 1.4.2. Ferromagnetic Layers

#### 1.5. Theoretical Radiation Tolerance of MTJs

## 2. Effects of Cosmic Radiation

#### 2.1. High-Energy Heavy-Ion Irradiation

#### 2.2. High-Energy Proton Irradiation

#### 2.3. High-Energy Neutron Irradiation

#### 2.4. High-Energy Electron Irradiation

## 3. Effects of $\mathbf{\gamma}$-ray Irradiation

#### 3.1. MTJ Materials under $\mathbf{\gamma}$-ray Irradiation

#### 3.1.1. MgO Crystals under $\gamma $-ray Irradiation

#### 3.1.2. Ferromagnetic Materials of MTJs under $\gamma $-ray Irradiation

#### 3.1.3. Interfaces of MgO Barrier/Ferromagnetic Layers

#### 3.2. MTJs under $\gamma $-ray Irradiation

#### 3.2.1. Sensitivity Results

#### 3.2.2. Tolerance Results

#### 3.3. Discussion of $\gamma $-ray Irradiation of MTJs

#### 3.3.1. $\gamma $-ray Penetration in MTJs

#### 3.3.2. Possible Explanations of Radiation Degradation

#### 3.3.3. Possible Explanations of Tunneling Tolerance

#### 3.3.4. Possible Explanations for Divergence

## 4. Effects of Lower-Energy Irradiation

#### 4.1. X-ray Irradiation

#### 4.2. UV–Vis Irradiation

#### 4.3. Infrared Radiation and Thermal Annealing

#### 4.4. Microwave Irradiation

#### 4.5. Radiofrequency Electromagnetic Irradiation

## 5. Outlook

## 6. Conclusions

## Author Contributions

## Funding

## Institutional Review Board Statement

## Informed Consent Statement

## Data Availability Statement

## Acknowledgments

## Conflicts of Interest

## Sample Availability

## Abbreviations

ADC | Analog-to-digital converter |

AMR | Anisotropic magnetoresistance |

CMOS | Complementary metal–oxide–semiconductor |

DC | Direct current |

DRAM | Dynamic random-access memory |

GMR | Giant magnetoresistance |

HDD | Hard disk drive |

MOS | Metal oxide sensor |

MR | Magnetoresistance |

MRAM | Magnetic random-access memory |

MTJ | Magnetic tunnel junction |

PV | Photovoltaic |

RAM | Random-access memory |

RF | Radiofrequency |

RT | Room temperature |

SEM | Scanning electron microscopy |

SRAM | Static random-access memory |

TE | Thermoelectric |

TEM | Transmission electron microscopy |

TMR | Tunnel magnetoresistance |

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**Figure 1.**Historical development of MR ratio of MgO-based MTJs at room temperature. The data of AlO-based MTJs are also plotted for comparison. Reproduced with permission [15]. Copyright 2008, the Physical Society of Japan.

**Figure 2.**(

**a**) TEM and (

**b**) HRTEM images of an Fe(001)/MgO(001)/Fe(001) MTJ. Reproduced [2]. Copyright 2004, Springer Nature.

**Figure 4.**Radiation (

**a**) in outer space and (

**b**) on Earth. Satellites are orbiting in the radiation zone of the Van Allen belts whose cross-sectional shape and intensity are shown in (

**a**). From nasa.gov (accessed on 7 August 2017).

**Figure 6.**(

**a**) Top view (along <001> direction) and (

**b**) side view (along <100> direction) of a MgO (001) monolayer.

**Figure 7.**Coupling of wave functions between the Bloch states in ferromagnetic Fe(001) layers and the evanescent states in the MgO(001) barrier for ${k}_{\Vert}=0$ direction. ${\Delta}_{1}:s-p-d$; ${\Delta}_{2}:d$; ${\Delta}_{5}:p-d$. Reproduced with permission [15]. Copyright 2008, the Physical Society of Japan.

**Figure 8.**Dose dependence of TL intensity of MgO nanomaterials irradiated by a pulsed electron beam. Reproduced with permission [157]. Copyright 2015, Elsevier Ltd.

**Figure 10.**Real-time capacitance versus $\gamma $-ray radiation dose for Ag/MgO/Ag capacitors. Replotted from Ref. [121]. Copyright 2005, Springer.

**Figure 11.**(

**a**) Thermal conductivity and (

**b**) spectra of optical absorption of MgO crystals before and after $\gamma $-ray irradiation. Reproduced with permission [163]. Copyright 1981, John Wiley and Sons.

**Figure 12.**(

**a**) TSL curves of MgO single crystals with OH${}^{-}$ impurity of $4.9\times {10}^{17}\phantom{\rule{0.277778em}{0ex}}/{\mathrm{cm}}^{3}$ under $\gamma $-ray irradiation under different temperatures. (

**b**) TSL intensity dependence of $\gamma $-ray irradiation dose at $450\phantom{\rule{0.277778em}{0ex}}\mathrm{K}$ [160]. Copyright 2011, David Publishing Company.

**Figure 13.**Temperature-dependent photoconductance per unit length of MgO polycrystals before, during, and after $\gamma $-ray irradiation [170]. Copyright 1975, Canadian Science Publishing.

**Figure 14.**M–H hysteresis loops of MgO-based MTJs measured in an in-plane magnetic field before and after irradiation with a TID of 20 Mrad (SI) [120]. Copyright 2019, IEEE.

**Figure 15.**Optical surface images of MgO-based MTJs (

**a**) before irradiation, (

**b**) after 20 Mrad (Si) irradiation, and (

**c**) after 247 Mrad (Si) irradiation [120]. Copyright 2019, IEEE.

**Figure 17.**(

**a**) Hysteresis loop of a single MgO-based MTJ and (

**b**) H${}_{c}$ and TMR of a series of MgO-based MTJs before and after exposure to $\gamma $-ray radiation with a dose rate of ∼$10\phantom{\rule{0.277778em}{0ex}}\mathrm{rad}/\mathrm{s}$ and energy of $1.25\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$. Inset: Illustration of the MTJ stack [152]. Copyright 2012, IEEE.

**Figure 18.**Transmission of electromagnetic radiation through an MTJ device. (

**a**) Structure [180] and (

**b**) HRTEM cross-sectional image [171] of an MTJ device used for penetration calculations of various types of radiation. Calculated radiation intensity through electrodes (

**c**) and sublayers (

**d**), including MgO barriers, under various radiation energies. The linear attenuation coefficients of the materials were obtained from https://www.physics.nist.gov (accessed on 17 September 2009). Reproduced with [180] with copyright 2010, Springer Nature. Reproduced with permission [171] with copyright 2016, American Chemical Society.

**Figure 19.**Transmission of $\gamma $-radiation through iron. ▲: ${}^{137}$Cs radiation of $0.66\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$; •: ${}^{60}$Co radiation of $1.17\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ and $1.33\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$; ■: ${}^{24}$Na radiation of $1.38\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ and $2.76\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$. Reproduced with permission [117]. Copyright 1953, American Physical Society.

**Figure 20.**Schematic illustrations of electron tunneling through (

**a**) a crystalline barrier and (

**b**) an irradiated barrier. ${\Delta}_{1}:s-p-d$; ${\Delta}_{2}:d$; ${\Delta}_{5}:p-d$. Replotted from Ref. [31]. Copyright 2007, IOP Publishing Ltd.

**Figure 21.**(

**a**) Effect of room temperature restoration of irradiated MgO powder measured with a delay period of 75 days ($t=75\phantom{\rule{0.277778em}{0ex}}\mathrm{d}$) and without a delay ($t=0\phantom{\rule{0.277778em}{0ex}}\mathrm{d}$). (

**b**) Relative thermoluminescence as a function of restoration time for irradiated MgO. Reproduced with permission [165] with copyright 2009, Taylor & Francis Group.

**Figure 22.**TL response of four MgO crystals as a function of UV exposure at 295 nm. Impurity of PA sample: <0.026; impurity of NA sample: 0.068; impurity of NB sample: 0.082; impurity of NC sample: <0.047. Reproduced with permission [186] with copyright 1976, Am. Assoic. Phys. Med.

**Figure 23.**Cross-sectional HRTEM images (

**a**–

**d**) and ADF-STEM images and corresponding elemental EELS mappings (

**e**–

**h**) using O-K, Fe-L${}_{3,2}$, Co-L${}_{3,2}$ and B-K ionization edges taken from the Ta/CoFeB/MgO/CoFeB/Ta MTJ (

**a**,

**b**,

**e**,

**f**) and W/ CoFeB/MgO/CoFeB MTJ (

**c**,

**d**,

**g**,

**h**) at $300{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ (

**a**,

**c**,

**e**,

**g**) and $400{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ (

**b**,

**d**,

**f**,

**h**). Reproduced with permission [193] with copyright 2018, Elsevier.

Name | Wavelength | Frequency | Energy |
---|---|---|---|

cosmic radiation | up to ${10}^{20}\phantom{\rule{0.277778em}{0ex}}\mathrm{eV}$ | ||

$\gamma $-ray | <0.01 nm | >30 EHz | >124 keV |

X-ray | 0.01 nm–10 nm | 30 EHz–30 PHz | 124.8 eV–124.8 keV |

UV | 10 nm–400 nm | 750 THz–30 PHz | 3.12 eV–124.8 eV |

visible | 400 nm–700 nm | 430 THz–750 THz | 1.872 eV–3.12 eV |

infrared | 700 nm–1 mm | 300 GHz–430 THz | 1.248 meV–1.872 eV |

microwave | 1 mm–0.1 m | 3 GHz–300 GHz | $1.248\phantom{\rule{0.277778em}{0ex}}\mathsf{\mu}\mathrm{eV}$–1.248 meV |

radio | >1 m | <3 GHz | <1.248 $\mathsf{\mu}$eV |

Sources | Type | Energy | Ref. |
---|---|---|---|

Cyclotron | heavy ions | 10 MeV | [111,112] |

EBIT | heavy ions | tens of keV | [112,113] |

Tandem accelerator | particles | 20–40 MeV | [112,114] |

FIB | gallium ions | 30 keV | [112] |

Nuclear reactor | neutron | 500 MeV | [115] |

TEM | electrons | 80–200 keV | [116] |

SEM | electrons | 5 keV–50 keV | [112] |

${}^{24}$Na source | $\gamma $-rays | $2.76\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$, $1.38\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ | [117,118] |

${}^{40}$K source | $\gamma $-rays | $1.46\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$, $1.31\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ | |

${}^{60}$Co source | $\gamma $-rays | $1.33\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$, $1.17\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ | [119,120] |

${}^{137}$Cs source | $\gamma $-rays | $0.66\phantom{\rule{0.277778em}{0ex}}\mathrm{MeV}$ | [121] |

Category | Unit | Definition |
---|---|---|

Activity | Becquerel (Bq) * | activity of a quantity of radioactive material in which one nucleus decays per second (1/s) |

Curie (Ci) | quantity or mass of radium emanation in equilibrium with one gram of radium (element), 1 Ci = $3.7\times {10}^{10}\phantom{\rule{0.277778em}{0ex}}\mathrm{q}$ | |

Rutherford (Rd) | activity of a quantity of radioactive material in which one million nuclei decay per second, 1 Rd = 1,000,000 Bq | |

Exposure | Röntgen (R) | quantity of radiation which liberates by ionization one esu ($3.33564\times {10}^{10}\phantom{\rule{0.277778em}{0ex}}$) of electricity per cm${}^{3}$ of air under normal conditions of temperature and pressure, 1 R = $2.58\times {10}^{-4}\phantom{\rule{0.277778em}{0ex}}/\mathrm{kg}$ |

Absorption | Gray (Gy) * | dose of one joule of energy absorbed per kilogram of matter, 1 Gy = 1 J/kg = 100 rad = 10,000 erg/gram |

Radiation absorbed dose (rad) | dose causing 100 ergs of energy to be absorbed by one gram of matter, 1 rad = 0.01 Gy = 100 erg/gram | |

Absorption | Sievert (Sv) * | equivalent biological effect of the deposit of a joule of radiation energy in a kilogram of human tissue, 1 Sv = 1 J/kg = 100 rem |

Roentgen equivalent man (rem) | unit of health effect of ionizing radiation, 1 rem = 0.010 Sv = 100 erg/gram | |

Dose | quantity of radiation or energy absorbed | |

Dose rate | dose delivered per unit of time | |

Exposure | amount of ionization produced by radiation, the unit is the roentgen (R). |

**Table 4.**Bulk properties of magnesium oxide (MgO) used as a barrier layers in MgO-based MTJs [105].

Physical Property | Values |
---|---|

Space group | Fm$\overline{3}$m, No. 225 |

Lattice constant | a = $4.212\phantom{\rule{0.277778em}{0ex}}\AA $ |

Cleavage | $<100>$ |

Molar mass | $40.3044\phantom{\rule{0.277778em}{0ex}}\mathrm{g}/\mathrm{mol}$ |

Coordination geometry | Octahedral (Mg${}^{2+}$) and octahedral (O${}^{2-}$) |

Density | $3.58\phantom{\rule{0.277778em}{0ex}}\mathrm{g}/{\mathrm{cm}}^{3}$ ($25{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Solubility in water | $0.0062\phantom{\rule{0.277778em}{0ex}}\mathrm{g}/\mathrm{L}$ ($0{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$), $0.086\phantom{\rule{0.277778em}{0ex}}\mathrm{g}/\mathrm{L}$ ($30{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Melting point | $2852{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ (3,125 K) |

Boiling point | $3600{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ (3,870 K) |

Thermal conductivity | 45–60 W/m/K ($25{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Thermal expansion | $138\times {10}^{-7}\phantom{\rule{0.277778em}{0ex}}{/}^{\circ}\mathrm{C}$ ($25{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Heat capacity (C) | $37.2\phantom{\rule{0.277778em}{0ex}}\mathrm{J}/\mathrm{mol}/\mathrm{K}$ ($24{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Std molar entropy (${S}_{298}^{{}^{\circ}}$) | $26.95\phantom{\rule{0.277778em}{0ex}}\mathrm{J}/\mathrm{mol}/\mathrm{K}$ |

Std enthalpy of formation (${\Delta}_{f}{H}_{298}^{{}^{\circ}}$) | $601.6\phantom{\rule{0.277778em}{0ex}}\mathrm{kJ}/\mathrm{mol}$ |

Gibbs free energy (${\Delta}_{f}{G}_{298}^{{}^{\circ}}$) | $-569.3\phantom{\rule{0.277778em}{0ex}}\mathrm{kJ}/\mathrm{mol}$ |

Electrical conductivity | ${10}^{-14}\phantom{\rule{0.277778em}{0ex}}\mathsf{\mu}\mathrm{S}/\mathrm{m}$ ($24{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$) |

Band gap | 7.8 eV [123] |

Refractive index (${n}_{D}$) | 1.7355 ($\lambda =0.633\phantom{\rule{0.277778em}{0ex}}\mathsf{\mu}\mathrm{m}$) |

1.72 ($\lambda =1\phantom{\rule{0.277778em}{0ex}}\mathsf{\mu}\mathrm{m}$) | |

Transparency | >92% ($\lambda $ = 0.25–7 $\mathsf{\mu}$m) |

Thermal stability | up to $700\phantom{\rule{0.277778em}{0ex}}\mathrm{K}$ |

Dielectric constant | 9.65 |

Magnetic susceptibility ($\chi $) | $-10.2\times {10}^{-6}\phantom{\rule{0.277778em}{0ex}}{\mathrm{cm}}^{3}/\mathrm{mol}$ |

Property | Fe | Co | (Co,Fe)${}_{80}$B${}_{20}$ |
---|---|---|---|

space group | Im$\overline{3}$m | P6${}_{3}$/mmc | amorphous [125] |

density (g/cm${}^{3}$) | 7.87 | 8.90 | 7.29 |

melting point (K) | 1811 | 1768 | 663–808 * [126] |

boiling point (K) | 3134 | 3200 | n/a |

thermal conductivity (W/m/K) | 80.4 | 100 | n/a |

electron configuration | [Ar]3d${}^{6}$4s${}^{2}$ | [Ar]3d${}^{7}$4s${}^{2}$ | n/a |

electric conductivity (S/m at RT) | $1.60\times {10}^{7}$ | $1.04\times {10}^{7}$ | ${10}^{6}$–${10}^{8}$ [127] |

magnetic moment (${\mu}_{B}$) | 2.2 | 1.6 | 2.1–2.5 [128] |

Curie temperature (K) | 1043 | 1388 | 631 |

MTJ Structures | Irradiation Conditions | Results | Ref. |
---|---|---|---|

CoFeB/MgO/CoFeB ${}^{\u2020}$ | Fe ions, 15 MeV, 400 MeV; Ar, 250 MeV; Kr, 322 MeV; Xe, 454 MeV; Os, 490 MeV | soft errors were detected | [151] |

CoFeB/MgO/CoFeB ${}^{\$}$ | ${}^{60}$Co, $\gamma $-ray, 247–475 Mrad, $220\phantom{\rule{0.277778em}{0ex}}\mathrm{rad}/\mathrm{s}$, room temperature | magnetism was destroyed | [120] |

CoFeB/MgO/CoFeB ${}^{\u266f}$ | neutron, 0.1 eV–10 MeV, $5\times {10}^{10}\phantom{\rule{3.33333pt}{0ex}}\mathrm{particles}\phantom{\rule{0.277778em}{0ex}}/\mathrm{c}{\mathrm{m}}^{2}/\mathrm{s}$, $2.9\times {10}^{15}\phantom{\rule{3.33333pt}{0ex}}\mathrm{particles}\phantom{\rule{0.277778em}{0ex}}\mathrm{c}{\mathrm{m}}^{2}$ | insensitive | [152] |

MTJ Structures | Irradiation Conditions | Results | Ref. |
---|---|---|---|

MgO crystals | $3.0\times {10}^{6}\phantom{\rule{0.277778em}{0ex}}\mathrm{rad}/\mathrm{h}$ for 20 min, ${}^{60}$Co, $38{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$, measured within 2 min after irradiation | irradiation produced vacancies | [162] |

MgO crystals | $\gamma $-ray, 2.1 MeV, up to 10 Mrad, $1.6\times {10}^{6}\phantom{\rule{0.277778em}{0ex}}\mathrm{rad}/\mathrm{h}$, RT | thermal conductivity decreased by half; absorption increased by five times; fully recovered after annealing at $625{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ for 1 h | [163] |

MgO crystals ${}^{\top}$ | $\gamma $-ray, $1.25\phantom{\rule{0.277778em}{0ex}}\mathrm{M}\mathrm{e}\phantom{\rule{-0.21251pt}{0ex}}\mathrm{V}$, $10\times {10}^{4}\phantom{\rule{0.277778em}{0ex}}\mathrm{Gy}$, 0.8 Gy/s, $450\phantom{\rule{0.277778em}{0ex}}\mathrm{K}$ | TSL intensity increased linearly with dose | [160] |

MgO crystals ${}^{\perp}$ | $\gamma $-ray, $1.25\phantom{\rule{0.277778em}{0ex}}\mathrm{M}\mathrm{e}\phantom{\rule{-0.21251pt}{0ex}}\mathrm{V}$, $10\times {10}^{4}\phantom{\rule{0.277778em}{0ex}}\mathrm{Gy}$, $0.8\phantom{\rule{0.277778em}{0ex}}\mathrm{Gy}/\mathrm{s}$, $450\phantom{\rule{0.277778em}{0ex}}\mathrm{K}$ | TSL intensity was very weakly dependent on dose | [160] |

MgO powder | $\gamma $-ray (${}^{60}$Co), $0.3\phantom{\rule{0.277778em}{0ex}}\mathrm{Mrads}/\mathrm{h}$, ∼$20\phantom{\rule{0.277778em}{0ex}}\mathrm{Mrads}$, stored at RT for 1 year before measurement | TL changed after irradiation | [164] |

MgO powder | $\gamma $-ray (${}^{60}$Co), $8.33\phantom{\rule{0.277778em}{0ex}}\mathrm{mGy}/\mathrm{s}$, $1\phantom{\rule{0.277778em}{0ex}}\mathrm{Gy}$–$50\phantom{\rule{0.277778em}{0ex}}\mathrm{kGy}$ | TL changed with dose | [165] |

Ag/MgO/Ag ${}^{\nabla}$ | $\gamma $-ray, 0.662 MeV, up to 32.55 mGy | capacitance increased with dose | [121] |

CoFeB films | $\gamma $-ray, 1.2 MeV, $2.58\times {10}^{5}\phantom{\rule{0.277778em}{0ex}}/\mathrm{kg}$, $60{\phantom{\rule{0.277778em}{0ex}}}^{\circ}\mathrm{C}$ | sensitive to $\gamma $-ray irradiation | [118] |

MgO/CoFeB ${}^{\S}$ | $\gamma $-ray, 100 kRad | no noticeable change in magnetic properties | [166] |

CoFeB/MgO/CoFeB | ${}^{60}$Co, $\gamma $-ray, 1 Mrad | no effect | [119] |

CoFeB/MgO/CoFeB ${}^{\P}$ | ${}^{60}$Co, $\gamma $-ray, 10 Mrad, 9.78 rad/min | highly tolerant of $\gamma $-ray radiation | [152] |

CoFeB/MgO/CoFeB ${}^{\u2021}$ | ${}^{60}$Co, $\gamma $-ray, below 20 Mrad, $220\phantom{\rule{0.277778em}{0ex}}\mathrm{rad}/\mathrm{s}$, RT | coercivity increased with irradiation while saturation magnetization was not affected | [120] |

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**MDPI and ACS Style**

Seifu, D.; Peng, Q.; Sze, K.; Hou, J.; Gao, F.; Lan, Y.
Electromagnetic Radiation Effects on MgO-Based Magnetic Tunnel Junctions: A Review. *Molecules* **2023**, *28*, 4151.
https://doi.org/10.3390/molecules28104151

**AMA Style**

Seifu D, Peng Q, Sze K, Hou J, Gao F, Lan Y.
Electromagnetic Radiation Effects on MgO-Based Magnetic Tunnel Junctions: A Review. *Molecules*. 2023; 28(10):4151.
https://doi.org/10.3390/molecules28104151

**Chicago/Turabian Style**

Seifu, Dereje, Qing Peng, Kit Sze, Jie Hou, Fei Gao, and Yucheng Lan.
2023. "Electromagnetic Radiation Effects on MgO-Based Magnetic Tunnel Junctions: A Review" *Molecules* 28, no. 10: 4151.
https://doi.org/10.3390/molecules28104151