JEOL Resources

Operando‐analysis of organic photovoltaic devices via ESR and EDMR methods

Tue, 01 Sep 2026 18:45:12 GMT

Application Note ER260006

Electron Spin Resonance (ESR) method is a useful technique which can detect polarons and trapped radicals as a change of magnetic moments, sensitively and selectively. In contrast, Electrically Detected Magnetic Resonance (EDMR, as shown in Fig. 2(b)) can selectively detect electron spins related to recombination currents, which are associated with device performance.

Symmetry evaluation of vacancy structure in silicon single crystal

Tue, 01 Sep 2026 18:40:51 GMT

Application Note ER260005

Information obtained from ESR measurements

Confirmation of the presence of defects
Evaluation of defect symmetry
Analysis of defect orientation
Evaluation of the electronic states of defects

Example of Measurements on a Silicon Single Crystal

We present an example of defect structure evaluation based on the angular dependence of ESR signals. In silicon crystals, the resonance magnetic field and the g-value of an ESR signal vary with the orientation of the external magnetic field relative to the crystal axes ([100], [110], [111], etc.). Analysis of this angular dependence provides valuable information about the symmetry and electronic structure of vacancy-related defects.

Power-Dependent Characteristics of Spin Current Transfer in Metal Bilayer Devices under High-Power Pulse Excitation

Tue, 31 May 2022 13:39:26 GMT

Abstract

The power-dependent transfer characteristics of spin currents generated at the interface of the permalloy/Pt bilayer device have been investigated over a wide power range from a few tens of milliwatt to 396 W. We built a high-power pulse excitation system for spin pumping, which achieves large electromotive force (EMF) values of 10 mV at 396 W excitation through the inverse spin Hall effect (ISHE) and demonstrates that the EMF generation after pulse excitation is very fast. Under strong pulse microwave excitation more than 80 W, the EMF spectrum exhibits an asymmetrical lineshape, which is well reproduced by simulations that take into account the fold-over effect due to the nonlinear ferromagnetic resonance excitation. The maximum output power at an external load through spin pumping and the ISHE is shown to increase in proportion to the square of the input microwave power (P_in) in the power range below 80 W. This power generation proportional to P_in² is unique to spin current-mediated power flow. In the strong excitation regime with the fold-over type EMF spectra, the EMF values of the peak magnetic field position are found to increase less linearly due to spectral broadening. This feature can be used for power generation that increases nonlinearly with respect to the input excitation power, where the nonlinearity is adjusted by varying the magnetic field position.

Please click this link to view the article: https://doi.org/10.1021/acsami.2c03418

Quantifying Power Flow Processes Mediated by Spin Currents

Fri, 30 Apr 2021 08:25:40 GMT

Abstract

The power flow process mediated by spin current in the bilayer device consisting of ferromagnetic metal (FM) and nonmagnetic metal (NM) layers is examined by realizing experimental evaluations for each process from the microwave absorption to electromotive force (EMF) output. The absorption power by ferromagnetic resonance (FMR) of the thin FM layer during the EMF output is directly measured in operando using an antenna probe system. The transfer efficiency of the absorption power into the NM layer by spin pumping is estimated from strict linewidth evaluation of EMF spectra. The maximum transfer efficiency of the spin pumping power to the external load via the inverse spin Hall effect is determined to be 4.2 × 10^–8 under 162 mW microwave irradiation using an analysis model assuming a parallel circuit. The main factors reducing the efficiency are found to be low resistivity of the NM layer and the interface loss. These quantifications are important as a first step to consider the efficient transfer of spin energy mediated by spin currents.

Click Link to Read More: https://doi.org/10.1021/acsaelm.0c01138

Strong interaction between light and electrons (4) "Transmission ESR/FMR measurement method"

Fri, 29 Jan 2021 13:23:22 GMT

Interaction between microwave photon and spins means in other words, interaction between resonating photon in a closing space and spins. Thus, measuring spectra using a non-resonant device can prevent the Purcell effect or strong coupling from distortion of intrinsic spectra. Figure 1(a) is a drawing expressing a typical spectroscopy. A light source irradiates light to a sample, and transmitted light is detected. A simple and non-resonant wave guide, as shown in Fig.1(b), can provide absorption spectra of para- and ferromagnetic samples which have a high spin density.

Fig.1　(a) A drawing of transmit absorption measurement. (b) An example of transmission ESR/FMR measuring device using a wave guide.

Transmission FMR spectrum

Spectra in Fig.2 are an FMR spectra of YIG-thin film (20μm thickness, conf. Application Note ER200008E ) using a detection device as shown in Fig.1(b). Merits of this method are that tuning of the filling factor and magnetic modulation are not necessary. Furthermore, dependence of FMR spectra on the frequencies is easily obtained. Application Note ER200010 will explain it more.

Fig.2　An example of transmission FMR spectra using YIG thin film.

Strong interaction between light and electrons (2) "Four states of interaction between photon and spins"

Fri, 29 Jan 2021 13:13:20 GMT

A conventional ESR spectrometer uses a cavity for microwave irradiation and detection of ESR absorption. On the resonance state, it can be considered as a model that spins absorb energy of ℎ𝜈=𝑔𝜇_𝐵𝐵 and then release it to the lattice system one way, where h: Planck constant, ν: frequency, g: g-value, μ_B: Bohr magneton, and B: magnetic flux density.
However, the interaction between photon of microwave and spins of electrons is a little more complex in fact.
Figure 1 is a modelized drawing that expresses energy flow of microwave photon and spins. The cavity resonates with angular frequency 𝜔_c, relaxes with velocity of 𝜅_𝑐=𝜔_𝑐/ 𝑄_𝑢, which is inversely proportional to unloaded Q value of the cavity. On the other hand, spins do precess with an angular frequency of 𝜔_𝑚= 𝛾_𝑒 𝐵_𝑚 under the static magnetic field 𝐵_𝑚.
When the resonant condition of 𝜔_𝑐= 𝜔_𝑚 is satisfied, excited electron spins that absorbed microwave energy relax with the velocity of 𝛾_𝑚(half width: half width at half maximum (HWHM)), which corresponds to spectral line width. At this time, photon and electron spins exchange energy with a coupling constant 𝑔_𝑚. The coupling constant 𝑔_𝑚 is expressed as^[1]

where 𝜂_𝑚^{𝑠𝑞𝑟𝑡} is the square root of the filling factor of the cavity, 𝛾_𝑒 is gyromagnetic ratio of the electron, ℏ is reduced Planck constant (h/2π), 𝜇₀ is vacuum permeability, 𝑉_𝑐 is the volume of the cavity, N is number of magnetic ions, and S is spin quantum number.

Fig.1 Energy flow in spin–cavity system.

Four states of interaction between photon and spins

Interaction between photon and spins can be categorized to four states according to the relation between the coupling constant (𝑔_𝑚), relaxation velocity (𝜅_𝑐) of photon, and relaxation velocity (𝛾_𝑚) of spins^[1].

『weak coupling』:
A state that corresponds to the condition of 𝑔_𝑚< 𝜅_𝑐 and 𝑔_𝑚 < 𝛾_𝑚. Normal ESR measurement is done in this state.
『Purcell effect』:
A state that corresponds to the condition of 𝑔_𝑚 < 𝛾_𝑚 and 𝑔_𝑚 > 𝜅_𝑐.
『strong coupling』:
A state that corresponds to the condition of 𝑔_𝑚 > 𝛾_𝑚 and 𝑔_𝑚 > 𝜅_𝑐. It behaves as a "quasi particle" that is unified by photon and spins.
『magnetically induced transparent (MIT)』:
A state that corresponds to the condition of 𝑔_𝑚 < 𝜅_𝑐 and 𝑔_𝑚 > 𝛾_𝑚.

Special care should be taken to the state of "Purcell effect" and "strong coupling", in practical ESR measurements.
Extraordinary spectral line shape, as shown in Application Note ER200006E , might be due to the interaction between microwave photon and spins. An excess sample amount would produce an unexpected effect according to this photon- spin interaction, because equation 1 indicates that coupling constant is proportional to the square root of spin numbers. As shown in Fig. 2, resonant frequency shift of the cavity (dotted lines corresponded to AFC balance) on measuring spectrum can help to check the abnormal interaction.

Fig. 2　Frequency shift of the cavity on measuring ESR spectra (conf. Application Note ER200006E ).

(a) Normal (Set_B). AFC balance does not almost move. (b) Excess sample (Set_A). AFC balance moves hard.

Investigating the frequency shift of the cavity around the resonant region, we can estimate what kind of interaction the system can be categorized to. Figure 3 is a mapping graph that the frequency spectra of the cavity ("Set_A" configuration as shown in Application Note ER200006E) is arrayed on the respective magnetic fields. Based on the simulation using the equation of Q-dip (S₁₁ parameter) shown in references^[2][3], coupling constant was estimated to ca 1.2 MHz. This situation is inferred to the state of "Purcell effect", because it is under the condition of 𝑔_𝑚/ 2𝜋 < 𝛾_𝑚/ 2𝜋 and 𝑔_𝑚/ 2𝜋 > 𝜅_𝑐/ 2𝜋 , where spectral half width (HWHM（half width at half maximum) is ca 121 μT (𝛾_𝑚/ 2𝜋=3.39 MHz), Q_u value of the cavity is ca 18,000 (𝜅_𝑐/ 2𝜋=0.52 MHz). Such a situation, normal ESR spectra can not be obtained. Especially, using high Q cavity that includes an excess sample might induce "Purcell effect", and it should be taken care of in the interaction. Furthermore, when the sample is not a paramagnet, but a ferromagnet, and its line width is narrow, we might encounter the state of "strong coupling" (continued to Application Note ER200008E ).

Fig.3　Field dependence of the frequency spectra (Q-dips).

(a) Observed. (b) Simulation results based on the equation in the literature^[3].

Reference: [1] X. Zhang, C-L. Zou, L. Jiang, and H. X. Tang, Phys. Rev. Lett. 113, 156401 (2014).
[2] E. Abe, H. Wu, A. Ardavan, and J. J. L. Morton,　Appl. Phys. Lett. 98, 251108 (2011).
[3] ] Patent, US10288707B2 "Relaxation time measuring method and magnetic resonance measuring apparatus".

Strong interaction between light and electrons (1) "Effect of excessive spins"

Fri, 29 Jan 2021 13:11:14 GMT

Typical electron spin resonance (ESR) spectrometer uses a microwave resonator, which is usually called a cavity, as a sensitive detector. A sample is usually set in the center of the cavity, and energy absorption by ESR phenomena is detected according to the degree of an impedance mismatching of the resonant circuit of the cavity. Absorption intensity in the ESR and FMR (Ferromagnetic Resonance) is proportional to the square root of the irradiated microwave power and the spin amount in the measured sample. Moreover, the spectral line width is proportional to the inverse of the transverse relaxation time of spins. The cavity is a device that stores only the light, of which the frequency is 𝜔_𝑐=2𝜋𝑓_𝑐, in the limited space. Electron spins lied in a static magnetic field are like spinning tops which are locked to specific Larmor frequency (𝜔_𝑟=2𝜋𝑓_𝑟). ESR/FMR spectrum is usually measured in the condition of 𝜔_𝑐=𝜔_𝑟. Recently, many attentions are gathering to the interaction between light (microwave) and spins in the cavity according to the development of quantum optics.

Sample and method

An 11.4 mg powder sample of 2,2-diphenyl-1-picrylhydrazyl (DPPH), which is used as a standard, loaded into a quartz tube with a diameter of 3 mm, and, as shown in Fig. 1(a), was set in the center position (Set_A) of the cavity. As another variation, the same sample was set in the edge (Set_B) of the cavity as shown in Fig. 1(b). Two ESR spectra of Set_A and Set_B were measured.

Fig.1 Sample set up in the cavity.

(a) Set_A: Sample set up in the center position of the cavity. (b) Set_B: Sample set up at the edge position (+27 mm) of the cavity.

Line width broadening by spin – cavity interaction

Two ESR spectra have apparent different line widths as shown in Fig.2, in spite of only changing the sample position in the cavity. Each spectrum is under a different condition of spin amount and magnetic flux density, but its spin concentration is the same. Therefore, the origin of different line widths cannot be explained simply based on the sample position. This is a basically different phenomena from the dipole-dipole interaction when spin concentration is low. Indeed, the normal spectrum is "Set_B". Spectral broadening like "Set_A" is called "radiation damping^[1]", and is sometimes a serious problem in an NMR measurement situation.

Fig.2 DPPH-ESR spectra at two different positions of the same sample.

Reference: [1] N. Bloembergen and R. V. Pound, Phys. Rev. 95, 8 (1954).

Strong interaction between light and electrons (3) "Strong coupling state of ferromagnetic thin film"

Fri, 29 Jan 2021 13:10:15 GMT

Coupling constant (𝑔_𝑚) between microwave photon and electron spins is proportional to the square root of spin numbers as shown in eq.(1) of "Application Note ER200007E ". Therefore, FMR measurements using ferromagnets which include many spins and especially have narrow line widths do not work well, because spins in ferromagnets interact strongly with microwave photon, and achieve to "strong coupling" state larger than the state of "Purcell effect". Figure 1(a) is an example that shows the obtained unexpected spectrum in the strong coupling state. Normal FMR spectrum can be obtained as shown in Fig.1(d), if the filling factor is reduced and the system moves to a "weak coupling" state.

Fig. 1　FMR spectral examples using ferromagnetic thin film (yttrium iron garnet（YIG）).

(a) Extraordinary spectrum obtained in the strong coupling state. (b) Sample position in the cavity. This produces a spectrum of (a). (c) Ordinary spectrum obtained in the weak coupling state. (d) Sample position in the cavity. This produces a spectrum of (c). (e) YIG thin film sample.

Frequency spectra of the cavity in "strong coupling" state.

Fig. 2　An example of frequency spectra of YIG-CMP system.

Figure 2 is a mapping chart that frequency spectra (Q-dip) of the cavity are arrayed on the respective measured magnetic fields. Different from the "Purcell effect", as closing to the resonant field, spectral peak splits to two and shifts repulsively. The coupling constant can be estimated as 𝑔_𝑚 ∕ 2𝜋 = 36 MHz from the splitting width of spectrum on the resonant magnetic field which an arrow indicates. This system is regarded as strong coupling state, because 𝑔_𝑚 is larger than k_c 𝑎𝑛𝑑 𝛾_𝑚, where Q_L is ca 8200 (k_c ∕ 2𝜋 = 0.55 MHz), and the spectral half width is ca 75 μT (𝛾_𝑚/ 2𝜋=2.1 MHz). The system that a cavity and a magnon belong to strong coupling state is called "cavity magnon polariton (CMP)". The CMP system is recently gathering a lot attention in quantum optics and quantum information, as an artificial quantum or quasi particle which is unified between microwave photon and spins of a magnon^[1].

Reference: [1] M. Harder and C.-M. Hu, Solid State Physics 69, 47 (2018).

JES-X3 Series (JES-X310 / JES-X320 / JES-X330) brochure

Tue, 28 Jul 2020 16:03:34 GMT

The ESR Spectrometer JES-X3 series has an improved low-noise Gunn oscillator, providing a 30% improvement in sensitivity compared to previous models. ESR is the only instrument for directly detecting paramagnetic species. This supports a variety of applications in research, development, inspection and evaluation.

JEOL Resources

Operando‐analysis of organic photovoltaic devices via ESR and EDMR methods

Application Note ER260006

Symmetry evaluation of vacancy structure in silicon single crystal

Application Note ER260005

Information obtained from ESR measurements

Example of Measurements on a Silicon Single Crystal

Power-Dependent Characteristics of Spin Current Transfer in Metal Bilayer Devices under High-Power Pulse Excitation

Abstract

Please click this link to view the article: https://doi.org/10.1021/acsami.2c03418

Quantifying Power Flow Processes Mediated by Spin Currents

Abstract

Click Link to Read More: https://doi.org/10.1021/acsaelm.0c01138

Strong interaction between light and electrons (4) "Transmission ESR/FMR measurement method"

Fig.1 (a) A drawing of transmit absorption measurement. (b) An example of transmission ESR/FMR measuring device using a wave guide.

Transmission FMR spectrum

Fig.2 An example of transmission FMR spectra using YIG thin film.

Strong interaction between light and electrons (2) "Four states of interaction between photon and spins"

Fig.1 Energy flow in spin–cavity system.

Four states of interaction between photon and spins

Fig. 2 Frequency shift of the cavity on measuring ESR spectra (conf. Application Note ER200006E ).

Fig.3 Field dependence of the frequency spectra (Q-dips).

Strong interaction between light and electrons (1) "Effect of excessive spins"

Sample and method

Fig.1 Sample set up in the cavity.

Line width broadening by spin – cavity interaction

Fig.2 DPPH-ESR spectra at two different positions of the same sample.

Strong interaction between light and electrons (3) "Strong coupling state of ferromagnetic thin film"

Fig. 1 FMR spectral examples using ferromagnetic thin film (yttrium iron garnet（YIG）).

Frequency spectra of the cavity in "strong coupling" state.

Fig. 2 An example of frequency spectra of YIG-CMP system.

JES-X3 Series (JES-X310 / JES-X320 / JES-X330) brochure

Fig.1　(a) A drawing of transmit absorption measurement. (b) An example of transmission ESR/FMR measuring device using a wave guide.

Fig.2　An example of transmission FMR spectra using YIG thin film.

Fig. 2　Frequency shift of the cavity on measuring ESR spectra (conf. Application Note ER200006E ).

Fig.3　Field dependence of the frequency spectra (Q-dips).

Fig. 1　FMR spectral examples using ferromagnetic thin film (yttrium iron garnet（YIG）).

Fig. 2　An example of frequency spectra of YIG-CMP system.